Archuleta

National Science Foundation

EAR-0073899

3D Inversion for Kinematic Earthquake Source Parameters

07/01/00-06/30/04

$186,564

The major focus of this proposal is to determine the kinematics of the earthquake rupture process on a finite fault by inverting seismic waveforms that include 3D earth structure.  With no direct observations of the earthquake process one must infer the spatial and temporal distribution of faulting by inverting the available data.  Determining the temporal parameters of the rupture process is fundamental to understanding earthquake physics.  An earthquake is a dynamic process during which the earth changes from one stress state to another by having two sides of the fault slip past each other.  As these two sides slip, seismic waves are radiated from the fault and are recorded at the earth’s surface.  Thus the recorded ground motion contains detailed information about how the slip evolved over the fault.  A kinematic description of the rupture process can be deduced by knowing the temporal distribution of the slip both in terms of when the slip is initiated and how it evolves to its final value for every point on the fault.  In short, the spatial distribution of both the rupture front and the slip—each as a function of time—must be known.

The rupture process on fault is deduced by iteratively fitting the synthetic (computed) ground motions to the data.  The Green's functions, i.e., the effect of earth on the passage of the seismic waves, play a critical role in the calculation of synthetic ground motion.  Although various numerical methods have been developed for the calculation of Green’s functions in a complex earth structure, the synthetic Green's functions used to invert for the kinematic rupture parameters have been calculated from 1D (horizontally-layered) geological models that do not account for the more realistic laterally heterogeneous earth structure.  While 1D approximations to earth structure can be justified in some cases, the omission of 3D structure on the seismic waves may significantly bias the rupture parameters determined from 1D inversions. It is now possible to include 3D wave propagation effects in the finite-fault inversions.  First the 3D structure of the earth is becoming better known through detailed investigations separate from this proposal.  Second, 3D finite difference (or finite element) methods can be used to calculate the Green's functions for complex earth structure. Including these 3D Green’s functions in inversions for the kinematic source parameters on a finite fault is a natural extension of current methods for determining the parameters of an earthquake rupture.

 

To further improve the inversions special functions (cubic B-spline) can be used to discretize the spatial distribution of the kinematic parameters on a finite fault.  Principal advantages of using cubic B-splines are their ability to represent a complicated structure with a small number of nodes and to assign the distribution of nodes so that the spacing between nodes is smaller in zones where the source parameters have the largest variations.  Thus, the resolution of the finite fault solution is improved without increasing the number of parameters.

 

The 3D Green’s functions and the cubic B-spline functions will be combined with a newly developed nonlinear inversion method that is necessary for a global search of the kinematic parameters needed to describe the rupture.  The proposed research is designed to extract the maximum information from the data to infer the nature of the earthquake rupture process by making use of the most current techniques in modeling and inversions.

 

Data from the California earthquakes 1979 M 5.9 Coyote Lake, 1989 M 7.1 Loma Prieta, 1994 M 6.7 Northridge, and the 1999 M 7.7 Chi Chi, Taiwan earthquake will be analyzed.  The 3D inversion results for the source parameters will be compared with those determined using 1D synthetic Green's functions. These inversions provide an opportunity to analyze the earthquake process in different tectonic settings and provide more insight into the underlying physics of ruptures in the earth.

Archuleta

University of Southern California

069203

ITR/AP:  The SCEC Community Modeling Environment:  An Information Infrastructure

10/01/01-09/30/03

$395,002

The first year’s efforts focus on simulating ground motion for scenario earthquakes in order to improve probabilistic seismic hazard analysis (PSHA)-Pathway 2 in the ITR proposal.  We will complete the validation of a three-dimensional viscoelastic finite difference (FD) code that can be used to simulate low-frequency ground motion for a wide range of scenario earthquakes.  This FD code will be wrapped and made available for execution on the web as a SCEC wave propagation community model.  The implementation will allow coupling to user-supplied rupture models as part of Pathway 3 in the ITR proposal.  Because the PSHA relies on high-frequency as well as low-frequency ground  motion, we will explore hybrid methods that can extend the frequency range of the computed ground motion to produce synthetic broadband time  histories.  For two scenario earthquakes we will compute multiple realizations of  broadband ground motion time histories from which statistical parameters can be computed.  These statistical parameters will be compared to estimates based on empirical methods used in PSHA.  

 

Archuleta

National Science Foundation

CMS-0201264

COSMOS Virtual Data Center

09/01/02-08/31/05

$397,395

The proposal requests support to continue development of the COSMOS Virtual Strong-motion Data Center — COSMOS VDC — an unrestricted, Web-based, interactive strong ground motion data resource for the practicing earthquake engineering, emergency response, research, and other earthquake professional communities.  The major goal of the VDC is to expand and significantly improve the accessibility and the use of all strong-motion records collected by the ever-growing number of US and international organizations (e.g. CDMG, USGS, ACOE, USBR, USC, SCEC, Japan KNET, Taiwan CWB, and others, including small networks operated by universities).  The VDC operates under the direction of The Consortium of Organizations for Strong-Motion Observation Systems (http://www.cosmos-eq.org/).  The COSMOS structure enables the VDC to respond to both the organizations that collect the data and the users (academic and professional) of the data; and ensures that the VDC evolves so that it remains responsive to the community of engineers, scientists and other users of strong-motion data.  This proposal is focused on advancing the science of interactive, Web-based analysis, dissemination, and use of strong-motion data for the direct benefit of the engineering and scientific communities who use the data to mitigate and understand the nature of earthquake hazards.  The proposed research will advance the capability of the COSMOS VDC by further developing the proven concept of a virtual data center and its important role in coordinating the access and dissemination of strong-motion data.

The VDC provides a very cost-effective way to leverage the data processing and management resources of all of the participating agencies and organizations.  The VDC continually develops, updates, and maintains a sophisticated parameter metadata environment in a state-of-the-art relational database.  This permits the user to interactively query, search, retrieve and analyze strong-motion information using the latest developments in Web technology.  At the same time, the accelerogram data and other data products are stored and maintained either by the collecting organization, or by the VDC, if the collecting organization so chooses, but in such a way as to be transparent to the user, thus the ‘virtual’ nature of the portal to the data provided by the VDC.  The direct responsibility for data collection, processing, basic quality control, and storage remains primarily in the hands of the collecting agencies and organizations. The user can thus have confidence that the data are the most current available.  This approach provides a major step forward in improving accessibility of the data to the research, practicing, and emergency response communities for purposes of earthquake hazard mitigation.

The funding sought by this proposal will be used together with funds provided by COSMOS to: 1) advance Web-based interfaces with the Advanced National Seismic System (ANSS) data management system; 2) advance methods for augmenting the existing VDC metadata database; 3) advance Web-based methods to facilitate efficient query and retrieval of a variety of event, station, and processed time history information; 4) develop Web-based methods for dissemination of information according to user selectable format, processing and visualization; 5) facilitate development of COSMOS standards for data formats and processing; 6) advance Web-based interfaces with other databases to enhance the metadata on earthquakes, recording site characteristics, and other relevant information for the VDC; 7) enhance Web-based interfaces and links for replication sites; and 8) advance Web-based interfaces with geotechnical databases.

Archuleta

National Science Foundation

EAR-0314367

Workshop:  Numerical Modeling of Earthquake Source Dynamics

06/15/03-05/31/04

$13,000

The goals of the workshop are:

to bring together the various researchers from America, Asia and Europe who use numerical simulations to investigate dynamics of the earthquake source

to communicate the state-of-the-art of the earthquake dynamics research

to provide a unique opportunity for in-depth discussions on earthquake dynamics

 

The workshop will be held August 31-September 4 at Smolenice Castle in the Slovak Republic.  This workshop is a joint collaboration among scientists from the US, Europe and Asia.  It is organized by a steering committee: Ralph Archuleta, Chairman, University of California at Santa Barbara, Santa Barbara, California, USA; Michel Bouchon, Université Joseph Fourier, Grenoble, France; Kojiro Irikura, Kyoto University, Kyoto, Japan, Raul Madariaga, École Normale Supériere, Paris, France; Peter Moczo, Comenius University, Bratislava, and Slovak Academy of Sciences, Bratislava, Slovak Republic.

 

The three days of talks and discussion will cover a full range of topics related to earthquake dynamics:

initial stress distributions on the fault

• nucleation of the rupture
• rupture propagation
• friction laws
• rupture arrests
• stress drops and scaling
• fault geometry
• material heterogeneity
• fault interaction
• energy budget and seismic radiation
• numerical techniques
• modeling real earthquakes

The Slovak Academy of Sciences and Comenius University will be hosts for this international workshop.  A website http://www.seismology.sk/NMESD2003.html announces the objectives, venue and logistics to the international geophysical community.  Because the space of the castle limits the number of participants, the number of US participants is limited to 20, Asia, 20 and Europe (including Russia) and Australia, 40. 

Archuleta

Department of Interior

03HQGR0053

Analysis of Data from the Yokohama Dense Array and its Applicability for

01/01/03-12/31/03

$70,393

Seismic microzonation is "the process of determining absolute or relative seismic hazard at many sites accounting for the effects of geologic and topographic amplification of motion and of soil stability and liquefaction, for the purpose of delineating seismic micro zones … in order to reduce damage to human life and property resulting from earthquakes." (EERI, 1984).  The intensity of the ground motion depends on the seismic source—earthquake magnitude distance from the seismic source, style of faulting—together with local soil conditions, topography and geological conditions.  The spatial variability of the ground motion, even over relatively short distances of hundreds of meters, is difficult to predict.  Peak amplitudes of acceleration or velocity can vary by a factor of five or more in several hundred meters.  Quantifying how factors such as soft soils, topography or geological conditions can affect the ground motion over small distances requires a large capital investment for instrumentation and an active seismic area that can provide a variety of different sources.  The 150 element Yokohama seismic array offers a unique opportunity to study the spatial variation of ground motion in a subduction zone setting.  The geological and tectonic setting of Yokohama is a natural analogue for Seattle.  In 1997 Yokohama established a dense accelerometer array to be used for mitigation of earthquake losses and real-time damage assessment.  The array is within a 434 km2 area with station spacing of approximately 2 km. In addition to the surface sites there are nine borehole sites, three of which are at depths around 62 m. We propose to analyze data from 29 earthquakes as recorded on this array.  Because of the density of stations we can correlate ground motion parameters such as spectral amplification, Arias intensity, duration, cumulative absolute velocity, peak ground acceleration and peak ground velocity with geological and geographical features such as basin depth, distance to basin edges and local shear wave velocity.  Rarely are there sufficient data to analyze the statistical variation in ground motion parameters over such a confined area.  The results of the analysis should provide insights into how different geological or geographical features affect ground motion.  Because of density of stations provided by the Yokohama array we can quantify the coherence of each parameter for different distances and correlate the same parameters with different geological conditions.  With the variety of different earthquake sources we can compare seismic sources that are crustal (less than 20 km deep) and those that are in the subducting slab (50-100 km deep).  Because of the tectonic and geological similarities between Yokohama and Seattle, we plan to transfer the findings from Yokohama to Seattle.  While we cannot have the same statistics in Seattle due to the more limited number of earthquakes and stations, the Yokohama analyses will suggest which parameters are likely to be more correlated with certain geological and geographical features of the Seattle area.  By applying the same analysis to data recorded in and near Seattle we will check this hypothesis.  The combined analysis of the Yokohama and Seattle data will provide a basis for microzonation of the Seattle area.  By including these results in land-use planning and in the design of structures and lifelines the costs of future earthquakes can be mitigated.

Archuleta

Nuclear Regulatory Commission

NRC-04-00-038

Garner Valley Downhole Seismographic Array

04/01/00-03/31/04

$548,000

The Garner Valley downhole seismographic array (GVDSA) is located in the Southern California between the San Jacinto and San Andreas faults.  The GVDSA test site is located in a narrow valley within the Peninsular Ranges Batholith.  GVDSA is located in a seismically active region 7 km from the main trace of the San Jacinto fault system and 35 km from the San Andreas fault.  The San Jacinto fault system has been historically the most active strike-slip fault system in Southern California. 

 

The San Jacinto fault has a slip rate of 10 mm/y (Sharp, 1967; Rockwell et al., 1990; WGCEP, 1995).  Based on historical seismicity and paleoseismological evidence Rockwell et al. (1990) argue that the Anza segment of the San Jacinto could produce an earthquake M 6.5-7.0.  Based on historical seismicity and paleoseismological data the 1995 Working Group on California Earthquake Probabilities (WGCEP, 1995) assigned a mean probability of 17% for a M 7.0-7.5 within the 30-year period 1994-2024 for the Anza segment. 

 

The Anza segment is 90 km long containing the Clark fault, Coyote Creek fault, and the Buck Ridge fault.  The next segment north of the Anza segment is the San Jacinto Valley segment.  WGCEP (1995) gave a 43% probability of a M 7.0 in the period 1994-2024.  The last known earthquake on this segment was a M 6.8 in 1918.  The Coachella Valley segment of the San Andreas has not had a major earthquake since about 1680 with an average recurrence interval of 220 plus or minus 13 yr.  The WGCEP (1995) assigned a probability of 22% of a M 7.5 in the period 1994-2024.  All of these studies reinforce the basic premise that GVDSA is located in an area where one should expect large amplitude ground motion from nearby major earthquakes. 

Becker

National Aeronautics & Space Administration

NAG5-13413

A Re-Examination of Nitrogen Heterocyclic Compounds in Extraterrestrial Samples

09/15/03-09/14/04

$80,000

The biological role of purines and pyrimidines as coding elements of ribonucleic acids (RNA) and deoxyribonucleic acids (DNA) have led to broad interest in the isolation, characterization and formation of these compounds and their related derivatives in meteorites (Folsome et al., 1971, 1973; Hayatsu (1964), Hayatsu et al., 1975; Van der Velden and Schwartz, 1977; Stoks and Schwartz, 1981 a,b, 1982; Pizzarello et al. 2001).  Geochemical studies of meteorites, especially Murchison, have provided some valuable clues about the mechanism of formation of other important organic compounds such as amino acids, via the Strecker-synthesis (Peltzer and Bada, 1978); however, attempts to establish a mechanism of formation for N-heterocycles remains problematic.

 

The problems encountered in some of the earlier work are, in part, due to very different approaches in isolating and analyzing these N-heterocycles in carbonaceous chondrites.  For example, Folsome (1971, 1973) examined charcoal absorbates of hot-water and hot formic acid extracts using GCMS and found mainly 4-hydroxypyrimidine, two isomeric methyl-4-hydroxypyrimidines and some non-biological compounds (e.g. pyrimidines, quinolizine).  Curiously, none of the biologically occurring purines or pyrimidines was detected.  This was followed up by Hayatsu et al. (1975) using both the Folsome et al. extraction method (1971, 1973) and much harsher extraction procedures (acid hydrolysis using 3-6 M HCL or trifluoroacetic acid) coupled to detection by direct probe MS without any further derivatization.  They detected aliphatic amines and C₂-C₆ alkyl pyridines but no 4-hydroxypyrimidines via the Folsome et al. (1973) method.  Using the stronger acids, two of the biological purines adenine and guanine were detected as well as the triazines melamine, cyanuric acid, urea and guanylurea, which have no known biological function.

Becker

Johns Hopkins University

862462

Organic Synthesis in Hypervelocity Impacts

11/15/02-06/30/05

$36,000

We propose to undertake a new study of the possible synthesis of pre-biotically relevant organic compounds in hypervelocity impacts.  The organic matter on planetary bodies originally derived from a combination of endogenous and exogenous processes, with impact shock and post-impact recombination playing a potentially significant role (e.g., Chyba and Sagan 1992, Nature 355, 125).  The inventory of organic species that may have resulted from recombining hypervelocity impact plasma remains somewhat speculative, especially for impacts above 20 km s-1 where current gun experiments cannot reach.  For airless small bodies and moons, such studies are important for comparison to, and in conjunction with, the important chemical processing of ices by UV radiation.  For planets with atmospheres, particularly Earth, such knowledge is needed to compare with the potentially complementary set of species synthesized in impact shock.  Pulsed laser ablation (LA) is a highly-promising experimental probe of this high velocity regime (e.g., Pirri 1977, Phys. Fluids 20, 221; Mukhin et al. 1989, Nature 340, 46).  A unique experimental design permits the study of LA products with both post-analysis of deposited films and high-sensitivity in situ time-of-flight mass spectrometry.  Initial results have shown that exobiologically-pertinent hydrocarbon oligomers with a wide range of energies and ionization states are produced even from a completely atomized plasma.  With this setup, and with an enhanced derivative design with improved control of laser coupling, energy, and spot-size, we will obtain a comprehensive analysis of the plasma recombination problem with standard carbon-matrix, meteorite, and carefully tailored ice analog materials.  Dr Becker will evaluate samples in her laboratory using LDMS and high performance liquid chormatography could to a photo-diode array detector to further evaluate the organ compounds formed in the hypervelocity impact experiments.

Becker

National Aeronautics & Space Administration

NAG5-11385

Fullerenes:  A New Carrier-Phase for Noble Gases in Meteorites

10/01/01-10/31/04

$86,139

The proposed project will address the hypothesis that fullerenes (pure carbon compounds with the simplest being C₆₀) are a major carrier phase for noble gases in meteorites.  The focus of this research will be to isolate and detect fullerenes and endohedral fullerenes (e.g. those with encapsulated noble gas atoms) in a suite of Antarctic meteorites including CM, CV, C2, CO3 L3.1, H3.3, CK4, CK5 and ureilites.  In addition, carbonaceous chondrites including the Allende, Murchison and Orgueil meteorites will also be examined.  The proposal for the Antarctic meteorites has been approved as part of a separate request to the Antarctic Working Group and will be analyzed as outlined in this study.  The objectives are:  (i) to ascertain how noble gases are retained in various carbon carriers (e.g. adsorption onto elemental and amorphous carbon vs. caged molecule trapping) (ii) to understand the processes that led to the formation of these molecules in the Cosmos; (iii) to measure the isotopic ratios of the trapped noble gases in this fullerene carrier phase to further assess the evolution of the early Solar system; (iv) and to re-evaluate the theories for ‘Planetary’ vs. ‘Nucleosynthesis’ to determine the origin of noble gases in planetary atmospheres.  Samples will be processed using established procedures outlined in previous investigations as well as some new techniques outlined in this proposal.

Becker

National Aeronautics & Space Administration

NAG5-11560

Interstellar Organic Molecules and the Origin of Life:  The Role of Exogenous

12/01/01-11/30/04

$180,249

Extraterrestrial bodies such as asteroids, comets and their associated dust, played a significant role in the early history of life on Earth and perhaps other planets.  The study of life under such extreme conditions requires knowledge of such fundamental issues as the nature of the organic material and the chemical processes that led to their formation in space, the chemistry of asteroids and comets, and the preservation of organics in the early terrestrial environment.  In this proposal we outline a program to examine the role of exogenous delivery of organic compounds to the early Earth by studying organic-rich meteorites (e.g. Muchison meteorite), sediments associated with giant impact events (Cretaceous/Tertiary ‘K/T’ boundary) and the inter-planetary dust (IDPs) found in deep-sea sediments (DSDP drilling cores).  We have developed several new techniques to search for specific organic tracers that will allow us to examine the contributions of exogenous delivery in providing complex organic compounds to the early Earth and to investigate the effects of such events on the biostratigraphic record over the past several million years.  Specifically, we will isolate fullerenes with trapped noble gases (Becker et al., 1996) and abiotic amino acids (a-AIB and isovaline; Zhao and Bada, 1989) in our samples and will compare the relative concentrations of these compounds to evaluate the preservation and accumulation of organics being delivered to the Earth.  In addition, we will carryout laboratory experiments to probe the level of chemical complexity that can be reached as a result of exogenous delivery and will examine the complexation of organic compounds to specific mineral phases.  Confirmation of the flux of extraterrestrial material in sediments throughout geologic time and its association with changes in the biostratigraphic record could have broad implications for the origin and evolution of life on the early Earth and perhaps other planets.

Becker

National Science Foundation

OPP-0229917

Collaborative Research:  Permian-Triassic Mass Extinction in Antarctica

06/01/03-05/31/04

$75,852

This proposal is to continue multidisciplinary studies of the fluvial sediments in Antarctica for evidence of what caused the greatest of all mass extinctions in the history of life at the Permian-Triassic boundary.  This boundary was until recently difficult to locate and thought to be disconformable in Antarctica.  New studies, particularly of carbon isotopic chemostratigraphy and of paleosols and root traces as paleoecosystem indicators, together with improved fossil plant, reptile and pollen biostratigraphy, now indicate the precise location of the boundary and have led to local discovery of iridium anomalies, shocked quartz, and fullerenes with extraterrestrial noble gases.  These anomalies are associated with a distinctive claystone breccia bed, also known in South Africa and Australia, and taken as evidence of deforestation.  There is already much evidence from Antarctica and elsewhere that the mass extinction on land was abrupt and synchronous with extinction in the ocean.

 

The problem now is what led to such death and destruction.  Carbon isotopic values are so low in these and other Permian-Triassic boundary sections that there was likely to have been some role for catastrophic destabilization of methane clathrates.  Getting the modeled amount of methane out of likely reservoirs would require such catastrophic events as bolide impact, flood-basalt eruption or continental-shelf collapse, which have all independently been implicated in the mass extinction and for which there is independent evidence.  Teasing apart these various hypotheses will require careful re-examination of previously discovered boundary beds, and search for more informative sequences, as was the case for the Cretaceous-Tertiary boundary.

 

This is collaborative research on geochemistry and petrography of boundary beds and paleosols (by Retallack), on carbon isotopic variation through the boundary interval (by Jahren) and on fullerenes, iridium and helium (by Becker).  Our primary field site for the first season is likely to be Coalsack Bluff in the central Transantarctic Mountains, with short visits also to Graphite Peak, Mt. Wild, Fremouw Peak and Mt. Boyd.  For the second season we plan to focus on Portal Mountain in southern Victoria Land, with short visits also to Mt. Crean, Mt. Fleming and Shapeless Mountain.

Boles

Department of Energy

DE-FG03-96ER14620

Fluid Flow in Faults:  Process and Effects from Modern and Paleo Systems

02/01/03-01/31/04

$234,971

We propose to expand our study of heat and mass transfer related to faulting.  Future studies will include estimating spatial distribution of fault permeability as indicated by diagenetic effects and determining  mechanisms and evolution of fluid movement.  Our work will continue to focus on transpressional sedimentary basins of southern California, which have been actively deforming since Miocene time

 

Specific questions to be addressed include: 

 

·      How does permeability of the fault system and associated fluid movement evolve over time?

 

·      What techniques are most effective at detecting thermal pulses in the fault environment?

 

·      What diagenetic evidence is there to support the hypothesis that fluid movement is episodic and rapid?

 

·      What are the geochemical and thermal implications of episodic fluid flow?

 

·      What evidence is there that solid earth tides affect fluid (gas) movement in fault systems and submarine seepage at continental margins?

 

The study of natural seepage along continental margins has become a frontier area for geofluids research (Parnell, 2002), yet we know of few groups like ours linking methods from hydrogeologic modeling and geochemistry/sedimentary petrology to problems of flow in faulted systems.  This is a true collaborative study combining field and analytical observations and data generated by the UC Santa Barbara team under the direction of James Boles with hydrogeologic and poroelasticity modeling generated by the Johns Hopkins University team under the direction of Grant Garven.

Burbank

National Science Foundation

EAR-0230403

Geologic Versus Geodetic Rates of Convergence in the Southeastern Tien Shan

03/01/03-02/29/04

$90,271

As geodetic studies yield increasingly precise representations of decadal patterns of crustal deformation, they pose intriguing problems that, in most sites, are unresolved at present.  Geodetically defined strain demands explanation:  Given a regional strain gradient, how is strain partitioned across the intervening terrain?  Do multiple structures accommodate the deformation, and, if so, how do they interact to produce the regional stain pattern?  Do geodetic strain rates at decadal scales provide a good representation of long-term strain rates, and, if so, at what spatial scales?  How far back in time can geodetic strain rates be extrapolated, and are they consistent with geologic data on the age of initial deformation and geologic  deformation rates through time?  Are regional rotational gradients defined by geodetic data consistent with rotations recorded by syntectonic strata?”

 

Several geodetic and geologic studies along strike-slip fault zones, such as the San Andreas, suggest that a reasonable match commonly exists between the geologic and geodetic data, such that the geodetic strain rates (Wdowinski et al, 2001; Hudnut et al, 2002) match the sum of documented geologic slip rates on known faults (Sieh and Williams, 1990; Weldon, 1996; Reheis and Dixon, 1996).  In contractional mountain belts, however, the correlations of short- and long-term strain rates (geodetic versus geologic) are more ambiguous. Similar geodetic strain gradients can be accommodated by very different structural patterns.  For example, across both the Kyrgyz Tien Shan (Abdrakhmatov et al, 1995; Reigber et al., 2001) and the Nepalese Himalaya (Larson et al, 1999; Wang et al, 2001), geodetic data define regional strain gradients of ~20 mm/yr of shortening.  Despite similarities in overall geodetic rates, the geologic data define striking contrasts in how this strain is accommodated.

Burbank/Archuleta

University of Southern California

075639-A

Radiated Seismic Energy from a Dynamic Faulting Model of the Northridge Earthquake

0/01/02-01/31/07

$22,000

We propose to compute the seismic radiated energy for the 1994 Northridge earthquake.  First, we will determine the initial stresses from the slip distribution using the method of Bouchon (1997).  The initial stresses will be based on the slip distribution derived by Liu and Archuleta (2002).  Because of a reduced budget we may not be able to consider the slip distribution derived by Wald et al., (1996).  From the stress distribution we will derive a spatially heterogeneous initial stress and yield stress.  The sliding friction stress will be fixed.  From this distribution of stresses and in concert with a slip weakening friction law we will dynamically rupture the fault.  The static stress drop will allow the computation of the elastostatic work available.  This work is partitioned into work spent during fracture (fracture energy and relaxation) and work radiated as seismic energy.  We will compute the radiated seismic energy as we have done for the 1979 Imperial Valley earthquake (Favreau and Archuleta, 2003).  This research will be carried out by Shuo Ma, a graduate student at UCSB under supervision by the principal investigator.

Burbank/Lavallee

University of Southern California

075639-0

Study and Modeling of Complexities of the Split Spatial Distribution for Large Earthquakes

02/01/02-01/31/07

$32,000

This project will pursue the investigation and quantification of complexities of the slip (or stress) spatial distribution for large earthquakes.  Priority will be given to earthquakes to be included in a database of References Earthquakes (see 2003 Program Announcement, Section VI.B.3).  Accordingly, we will start with the analysis of the slip spatial heterogeneities of the 1992 Landers earthquake and follow with the slip spatial heterogeneities of the Northridge earthquake.  If the slip or stress spatial distribution of the Hector Mine earthquake of 1999 is made available in the coming year, it will be considered in this investigation.  Other earthquakes (listed in Section 1.2 of the proposal) will be included in this investigation if time allows.  The method used to investigate the slip spatial heterogeneities are described in Section 1.2 of the proposal.

 

Following the recommendations of the SCEC Panel Summary, more attention will be paid to the consequences that the scaling law observed for the slip power spectrum at low wave number may have when extrapolated to higher wave number.  Also in the future, special efforts will be made to make scientific communications, including the annual report and the proposal, less obscure and more comprehensible for the non-initiated readers.  In particular, I will do my best to clarify the discussion about non-Gaussian random variables – such as the Levy random variables.

Burbank/Liu

University of Southern California

075639-P

Quantifying Uncertainty in Finite Fault Inversions

02/01/02-01/31/07

$20,000

In our original proposal we included the following statements of work:  1) estimate the uncertainty in the finite fault solution using the bootstrap method, 2) examine the effect of different objective functions on the finite fault inversion, 3) apply our approach to the data from the 1994 M 6.7 Northridge earthquake, 4) use a hybrid technology in the bootstrap process of analyzing the data.  The bootstrap process would use the global inversion method (Liu and Archuleta, 2000) and the original data set to invert for a best source model.  This solution is then chosen as starting model, and a linearized iterative inversion technique (Hartzell, 1989) would be applied to invert bootstrap data samples.

 

With the modified budget we will do the proposed work with a significant modification.  We will not adapt the bootstrap method to the linearized iterative inversion technique of Hartzell (1989).  Instead we still use our global inversion method (Liu and Archuleta, 2000) in the whole bootstrap process.  This adjustment will not affect the basic objectives of the proposal.  It reduces the time for the researcher supported by this proposal; however, the computer time to complete the work will increase significantly which may limit the number of parameter studies that can be done.

Burbank/Olsen

University of Southern California

075639-Q

Estimation of LA Basin Seismic Wave Amplification Effects

02/01/02-01/31/07

$20,000

We propose to continue ongoing work comparing ground motion computed by prescribed and dynamic rupture propagation for dipping faults buried up to 5 km (Gottschammer and Olsen, 2001).  We use a fourth-order finite-difference (FD) method and the mixed boundary condition with a rate- and slip-weakening friction law.  The numerical grid is parallel to the fault plane with the free surface at an angle with respect to the numerical grid by introducing a vacuum layer.  Preliminary results for a 45 degree dipping thrust fault suggest that inclusion of these effects increases the peak displacements and velocities above the fault significantly by including the increase in moment due to normal-stress effects at the free surface (see Fig 1. of Progress Report:  How Can We Improve Ground Motion Estimates by Lessons Learned from Rupture Dynamics?).  The results suggest that dynamic interaction with the free surface can significantly affect the ground motion for faults buried less than 1-3 km.  We believe that the proposed research can help delineate the range of effects that may be expected in a realistic earthquake scenario.

 

We propose to continue the work by (Gottschammer and Olsen, 2001) by comparing prescribed and spontaneous dynamic rupture propagation on dipping thrust faults buried 0-5 km in half-space and realistically layered models, as well as ground motions on the free surface for frequencies less than 1 Hz.  The comparisons include dynamic simulations using a 3D FD method with rate-and-state friction on a planar fault in a realistically layered medium.  In the continuation of the project proposed here we will test the effects of using more realistic heterogeneous dynamic rupture parameters, as well as variation of the stress level in the near-surface material.  We will continue testing the findings that ground motions from buried faulting are consistently stronger than that from earthquakes having large surface slip (Somerville, 2000), for heterogeneous distributions of rupture parameters.

Burbank/Olsen

University of Southern California

075639-R

Estimation of Dynamic Rupture Parameters

02/01/02-01/31/07

$15,000

We propose to continue to develop, implement and test a systematic inversion method to estimate rupture propagation and the underlying dynamic parameters for large historical earthquakes using the Neighborhood algorithm (NA).  We will test the efficiency and limitations of the method on realistic fault models.  The tests include estimating the number of parameters that can be reliably determined, the dependence of the initial model, of the control parameters of NA and selection of rupture parameters (i.e., stress, friction, or rupture energy), the need for constraints on the rupture parameters, and rate of convergence.  We will implement ways of speeding up the convergence of the method, including ‘early detection’ of ‘poor’ models, for example those where rupture does not initiate.  We will optimize the finite-difference forward modeling method in terms of RAM and cpu-time requirements.  To achieve this goal, we plan to use the efficient Perfectly Matched Layers (PML) absorbing boundary conditions (Marcinkovich and Olsen, 2003).

 

We propose to examine in detail the constraints that near-fault strong motion records can provide for the slip-weakening distance (Mikumo et al., 2003).  In particular, we propose to investigate the resolution of D_c.  We will estimate D_c from near-fault ground motions for the 1979 Imperial Valley and 2002 Denali earthquakes.  We will examine the radius of influence from the fault on near-fault strong motion records in order to address the severity of the averaging process controlling the estimate of D_c.  Finally, we propose to estimate the effect of different kinds of slip-weakening behavior on the resolution of the method.

Burbank/Oskin

University of Southern California

075639-T

Implementation of the SCEC Community Vertical Motion Map

02/01/02-01/31/07

$10,000

This Geologic Vertical Motion Database (GVMD) and vertical motion map utility will be developed and maintained at the Institute for Crustal Studies at the University of California, Santa Barbara.  Similar in organization to existing databases of fault geometry (CFM), fault activity (FAD), crustal motion (CMM) and seismic velocity (CVM), the GVMD and vertical motion map utility will be an on-line, maintained, and documented resource available to the scientific community.

 

N. Niemi and M. Oskin will each devote two months to completion and testing of the GVMD and vertical motion map utility.  Niemi and Oskin are both geologists experienced with Arc/Info GIS and familiar with object-oriented programming languages and database-driven web applications.  Niemi has been programming in ArcGIS for the past year full time as academic staff at the Massachusetts Institute of Technology.  Population of the GVMD with available geologic data will take advantage of the variety of experience and resources available at the Institute for Crustal Studies at the University of California, Santa Barbara.  C. Sorlien will aid in planning of the database structure and entry of marine geologic subsidence and uplift data from onshore and offshore basins.  Oskin will devote one additional month to entry of onshore tectonic geomorphology and thermochronology uplift data.

Burbank/Liu

University of Southern California

075639-C

Resolution and Stability Analysis of Finite Fault Inversions

02/01/02-01/31/07

$20,000

Since the original inversions of strong motion data by Trifunac and Udwadia (1974), there have been a vast array of inversion methods applied to near-source ground motion records.  Correctly determining the kinematics parameters of the rupture process is fundamental to our understanding of earthquake physics.  The kinematic parameters obtained from an inversion can be used to infer the stress drop distribution (e.g., Mikumo and Miyatake, 1995; Bouchon, 1997; Day et al., 1998) that in turn can be used as the input for dynamic models (e.g., Olsen et al, 1997; Nielsen and Olsen, 2000; Archuleta and Favreau, 2001).  The kinematic parameters have been used to infer scaling properties (e.g., Somerville et al., 1999; Mai and Beroza, 2000) and as input to finite difference codes in an attempt to determine frictional parameters (e.g., Ide and Takeo, 1997).  Of course, the spatial and temporal distribution of source parameters is critical in forward modeling of ground motion.  As such the inversions serve as a baseline for the range of parameters that are plausible in predicting ground motions for engineering design purposes.

 

Methods for inverting the data usually require parameterization of the faulting process by dividing the finite fault into a grid of small cells or subfaults and approximating the ground motion at a given station by a linear sum of the synthetics originating from these subfaults.  There is no criterion to decide how large a subfault should be.  Several papers show that changes in the size of subfaults can have a significant effect on a finite-fault inversion (Hartzell and Langer, 1993; Das and Suhadolc, 1996).  In a similar vein there is a wide range of objective functions that are to be minimized in the process of comparing synthetic time histories with the data.  It is unclear how the choice of an objective function affects the inversion results.  The rupture process on the fault is deduced through iteratively fitting the synthetic time histories to recordings (by use of the objective function).  Obviously the solutions obtained from this inversion process will depend on the Green’s functions because they are essential to the representation theorem used to compute synthetics that are compared to data.  With the recent advent of efficient 3-D numerical wave propagation methods and improved knowledge about the crustal structure, it is now possible to invert for kinematic parameters of a finite fault using Green’s functions computed from a 3-D structure.  Do 3-D Green’s functions improve the resolution of kinematic source parameters?

 

This proposal focuses on three elements of finite fault inversion methods:  1) influence of subfault size; 2) choice of objective function for minimizing the difference between synthetics and 3) effectiveness of 3-D Green’s function in determining the kinematic parameters of faulting.

Burbank/Sorlien

University of Southern California

075639-U

Contributions to the SCEC Community Fault Model:  Relating Onshore-offshore Stratigraphy and Fault-Fold Activity Beneath Santa Monica Bay

02/01/02-01/31/07

$20,000

This study proposes to utilize high resolution and industry seismic reflection data, well and seafloor geologic data, and swath bathymetric and backscatter data to investigate Quaternary deformation.  We will correlate strata from ODP Site 1015 in Santa Monica bathymetric basin north to the Shelf Projection Anticline, and to sets of 800 X 2500 m grids of high-resolution reflection data that cross both the Dume segment of the Santa Monica fault and the San Pedro Basin fault and related folds.  Ongoing NEHRP-supported structure-contour mapping of the top Miocene and top Repetto Formation horizons will be extended to include one or more late Quaternary horizon as they are identified by correlation to onshore stratigraphy, and by biostratigraphic interpretation of a detailed list of benthic foraminifera for an offshore well.  Several approaches will be used to correlate pre-latest Quaternary stratigraphy to the south of the Shelf Projection, possibly by regional correlations to wells offshore Redondo Beach, by correlation to our existing stratigraphic interpretations west and north of the Shelf Projection, or even correlating south of Palos Verdes (the Beta Field area).  Activity on high-angle faults can be determined from vertical separation of a given horizon, and activity on folds can be determined by thinning and onlap of strata onto the fold.  We will also incorporate submarine geomorphology using multibeam bathymetry and backscatter data, combined with high-resolution seismic reflection data.  After the active faults and folds are identified and their kinematics interpreted, we can model the interactions between folding and blind thrusting, as well as strike-slip faulting.  In this way the post-4 Ma average displacements can be related to modern deformation and seismicity.

Burbank/Steidl

University of Southern California

075639-L

SCEC Borehold Instrumentation Program

02/01/02-01/31/07

$25,000

One of the major goals of the Center is to compute theoretical seismograms for scenario earthquakes in the Los Angeles and Southern California region.  Existing strong-motion data are used to calibrate and improve our computational techniques.  Ground motions recorded at strong motion stations throughout Southern California are a combination of the complex earthquake source process, the propagation path from the source zone to the station, and the local near-surface site conditions at the station.  Separation of source, path, and site effects is limited by the current availability of data, the lack of detail in our knowledge of the crustal structure, and our understanding of the earthquake source process.  Widespread and varied ground motions and damage patterns over short distances produce a large degree of uncertainty in our ability to predict ground motion from future earthquakes.  In order to reduce the uncertainty in our theoretical seismograms of possible scenario earthquakes, we will observe and remove the near-surface site effect at a few select stations having “typical” southern California soil profiles by using borehole instrumentation.  Observations from the SCEC borehole project allow for direct estimation of site effects, provide a test for the calibration and improvement of physical models of soil response, and give us a clearer picture of the incident ground motion that can then be used to study in more detail the earthquake source process and the regional crustal structure.

 

Much of the variability mentioned above is caused by the local near-surface site conditions and shallow crustal structure.  The upper several meters to several tens of meters in the geologic section have major influence on amplification or deamplification of seismically generated ground motions and the initiation of ground deformation or ground failure.  Evaluation of ground response and ground deformation in these upper layers, and the interaction with foundations and structures, is a critically important aspect of safe and economical engineering design.  One of the primary goals of SCEC is to generate analytical and empirical models for accurate prediction of ground response and ground deformation due to earthquakes.  A required element for the development of these models is well-instrumented field sites where actual ground response and deformation can be monitored during earthquake shaking to provide benchmark case histories for model development and verification.  Records from a number of sites with a variety of soil types and geometric configurations are needed to provide a range of site conditions commensurate with those commonly encountered in engineering design.

 

Under this proposal, the SCEC borehole instrumentation program will continue ongoing efforts to increase the number of these benchmark sites in the Southern California region (currently nine) and to make the data available in real-time through the SCEC data center.  We will continue to use the data to develop the numerical techniques for linear and nonlinear site response analysis, dynamic modeling of soil behavior at large strain, and analysis of source and path properties.  We will seek out new targets of opportunity to provide observations from deep rock sites in close proximity to active faults.  Collaborations with other agencies will continue to allow us to stretch the SCEC dollar and provide significant value for the cost.  We will also contribute to the short-term goals of the implementation interface group through a newly formed collaboration with our engineering colleagues and the NSF engineering funded George E. Brown Jr. NEES program.

Burbank

National Science Foundation

0229911

Collaborative Research:  Extrusion and Rotation During Intracontinental

02/15/03-01/31/06

$52,985

Despite recent advances in our understanding of the mechanical and thermal response of

continental lithosphere to collisional orogenesis, important controversies remain.  One of these

centers on the role of large strike-slip faults during intracontinental deformation, and whether these

structures 1) control the lateral ‘escape’ of quasi-rigid blocks in response to continental convergence

(e.g., Tapponnier et al., 1982), or 2) reflect the passive localization of strain in a pervasively

deforming and shearing crust (e.g., England and Molnar, 1990).  The models make very different

predictions regarding the variation of displacement along strike-slip faults, the relationship of fault

displacement to deformation of the surrounding crustal blocks, and the nature of accommodation of

slip at the terminations of the faults.  In eastern Tibet, continuing debate over the nature of active

deformation reflects, to a large degree, the limited number of rigorous geologic tests of these

predictions.

 

The Kunlun fault is a first-order structural feature in the central and eastern Tibetan Plateau,

where it presents a key opportunity to test among competing hypotheses for the role of strike-slip

faults in the active deformation of eastern Tibet.  Although Holocene slip rates appear to be uniform

at ~11mm/yr along the central portion of the fault (Van der Woerd et al., 2000), several

observations suggest that significant left-lateral shear along the eastern Kunlun fault does not reach

the margin of the Tibetan Plateau:  1) the active trace of the fault on remote sensing (e.g.,

Tapponnier and Molnar, 1977) cannot be distinguished east of ~102°E; 2) field observations (Kirby)

confirm that scarps associated with the Kunlun fault are not present east of this region; and 3)

geodetic surveys indicate that, at present, little resolvable left-lateral shear passes through the eastern

margin of the plateau (Chen et al., 2000).  Determining what happens to left-lateral shear along the

easternmost portion of the Kunlun fault is critical if we are to understand its kinematic and dynamic

role in deformation of eastern Tibet and more generally the role of strike-slip faults during

intracontinental deformation.

 

We propose to test several hypotheses regarding the mechanisms of transfer and/or

accommodation of displacement at the apparent termination of an intracontinental strike-slip fault:

• Hypothesis 1:  Displacement is transferred to kinematically linked, strike-slip faults that:

1. transmit displacement across and beyond the plateau margin, or
2. transmit displacement to shortening structures at the plateau margin.

• Hypothesis 2:  Displacement is absorbed by distributed shortening within the plateau resulting

in crustal thickening.

• Hypothesis 3:  Displacement represents passive rotation of faults in response to a diffuse,

clockwise regional shear.

 

Testing these hypotheses will focus on the following tasks:

• Determining Late Pleistocene-Holocene slip rates along the easternmost segment of the Kunlun

fault, with special attention to potential variations along strike.

• Establishing the geometry, kinematics, and rates of displacement on candidate accommodation

structures (both within the plateau and at its margin).

• Assessing the magnitude and distribution of differential rock uplift and river incision in the

Anyemaqen Shan (the prime candidate for shortening within the plateau)

This study promises to bring a detailed chronologic perspective to bear on the nature of

accommodation of strain at the terminations of large, intracontinental strike-slip faults.  We will

document the presence or absence of displacement gradients present near the ends of such structures.

The study will define the relationship of fault displacement to regional deformation patterns and will

determine some of the mechanisms by which displacement is transferred to other structures.  Finally,

it will determine to what degree fault displacements are linked to deformation of the bounding

blocks.  The combined results will yield critical new insights into the problem of extrusion versus

rotation during continental deformation.

Burbank/Oskin

University of Southern California

075639-S

Fault Versus Off-Fault Deformation of the Eastern California Shear Zone

02/01/02-01/31/07

$20,000

Field mapping of the Black Mountains basalt field will extend existing basalt flow stratigraphy east and west of the Blackwater fault.  The goal of this field mapping is to determine (1) a piercing line across the Gravel Hills fault, (2) an inventory of secondary faults and folds between the Gravel Hills and Blackwater faults, and (3) a stratigraphy of individual flow units distributed across the length of the Black Mountains basalt field.  Faults will be mapped through combined fieldwork and analysis of remote sensing data.  Fault offsets will be surveyed in the field and the results of this mapping will be compiled as an Arc/Info database and map.

Burbank/Archuleta

University of Southern California

075639-B

SCEC Strong Motion Database

02/01/02-01/31/07

$29,999

By this proposal we are requesting funding to continue development of the COSMOS Strong-Motion Virtual Data Center – (COSMOS VDC) – an unrestricted, web-based, interactive strong ground-motion data resource for practicing earthquake engineers, emergency response and recovery agencies and officials, researchers, and other earthquake professionals.  The urgent need for effective and efficient access to strong-motion data has been well documented.  Through the foresight of the agencies that have deployed and operate strong-motion networks there now exists an abundance of data.  With the increasing deployment of digital recorders with high dynamic range such as TRINET, ANSS, and KNET, we can expect a continuing increase in the rate of data recorded.  However, the full impact of the strong-motion data on public safety in earthquakes depends on their accessibility to the engineers, seismologists, and other users.  With the basic goal of providing practicing earthquake professionals and public officials efficient, routine access to strong motion data as part of their practices, COSMOS has developed the VDC (http://db.cosmos-eq.org/).

 

The natural venue for this access is through the World Wide Web, which provides the means to retrieve data from any type of computer, view and copy plots and maps to the user’s computer, etc.  The universality of the Web allows equal access to all of the engineering and seismological communities, to large companies as well as university consortia.  The VDC allows the user to search for and select the data most appropriate for a particular project or application, based on the individual user’s needs.  The VDC is the only strong-motion data center that is attempting to provide access to all strong-motion data on-line.

Burbank/Steidl

University of Southern California

075639-V

Attenuation Analysis of Borehold Data for CVM

02/01/02-01/31/07

$25,000

The method used in this project will be nonlinear waveform inversion.  The model parameters to be determined in the global inversion method developed by Liu et al. (1995a, b) are Q_o and P, where the attenuation is defined as Q(f) = Q₀f^p .  We assume this standard functional form for the frequency dependence of Q and use the global inversion to determine the dependence on a site-by-site basis.  The exponent P is bounded by the two end member cases where P = -0.5 and P = 0.5.  It is possible to invert for other material properties using this global inversion scheme; however, we will fix the other material properties using the independent site characterization data at these sites and focus solely on attenuation.

 

The forward model will be calculated using a modified 1D Haskell tranfer matrix that incorporates the ability to accurately include frequency dependence of attenuation.  The synthetics will be generated using the borehold data as the input.  Surface observations and synthetics will then be transformed into the wavelet domain for the global inversion.  We have had success in the past in modeling waveform data from borehole arrays to frequencies of up the 10 Hz (Steidl et al., 1998).  Initial inversions will span the frequency range of 0.1 to 10 Hz, and depending on the results, we may attempt to push the upper frequency limit higher, or alternatively, compute a high frequency inversion in the frequency domain, matching spectra instead of waveforms.

Burbank/Nicholson

University of Southern California

075639-D

Building the SCEC 3D Community Fault Model:  Onshore Western Transverse Ranges and Ventura Basin

02/01/02-01/31/07

$38,000

The purpose of this proposal is to produce digital 3D structure contour maps of active fault surfaces for input into the SCEC high-resolution community fault model (CFM-B).  The primary faults we will be concerned with include the major faults of the onshore western Transverse Ranges and Ventura basin.  This includes the onshore Oak Ridge, Red Mountain-Pitas Point, San Cayetano, Santa Susana, Santa Ynez, and Arroyo Parida-Mission Ridge faults.  This work will tie directly with similar ongoing studies in the offshore Santa Barbara Channel and Santa Monica Bay (Kamerling and Nicholson, 1995; Kamerling et al, 2001; Sorlien et al, 2001).  Fault surfaces will be defined in 3D based in integrating seismic reflection, seismicity, gravity, topography, surface mapping, and well data.  Variations in possible interpretations of 3D fault surfaces will also be documented.  For example, there are currently 5 published interpretations for the shallow (upper 3 km) geometry of the San Cayentao fault alone (Hester and Truex, 1977; Cemen, 1989; Namson and Davis, 1991; Hopps et al., 1992, Huftile and Yeats, 1996).

Burbank/Tanimoto

University of Southern California

075639-W

Testing and Improving the SCEC Community Velocity Model 3.0 with TriNet Broadband Data

02/01/02-01/31/07

$25,000

Broadband seismic data from TriNet provides an excellent opportunity to test the SCEC Community Velocity Model 3.0 (SCEC CVM 3.0; Kohler et al., 2002).  Our preliminary analysis in the first year indicated that surface waves for frequencies about 20-50 mHz are not fit by the CVM 3.0.  We propose to analyze teleseismic surface waves and body waves recorded by TriNet and to construct an improved model.  The ultimate purpose is to construct a model of large-scale 3D structure in Southern California which will serve as a good reference model.  The resulting model will enhance the CVM 3.0 in many ways.  For example, S-wave velocity structure in the crust and mantle will be better constrained because of the addition of surface wave data to the body wave data.  The model will provide an extension into the oceanic region because of new TriNet stations and the accumulation of island station data.  The model will also expand the mantle region covered by the CVM 3.0.  The mantle in the CVM 3.0 spans a region smaller than the crustal region.  The model will provide a well-constrained overview of long-wavelength features in the entire Southern California region and thus will help us understand the overall tectonic features.  Our preliminary maps contain some surprising features that will potentially lead to a new understanding of large-scale tectonics in this region.

Burbank/Olsen

University of Southern California

075639-E

Direct Measurement of the Slip-Weakening Distance from Near-Fault Strong Motion Data

02/01/02-01/31/07

$20,000

The proposed research is inspired by the request from two different Focus Groups to analyze the nature of friction, in particular using information from radiated waves emitted by the earthquake rupture (Goals 3d and 4c).  Here, we propose to investigate in detail to which extent one of the most important frictional parameters controlling earthquake rupture propagation, the slip-weakening distance D_c, may be estimated directly from near-fault strong motion records for steeply-dipping shear faults.  Preliminary results using numerical dynamic rupture simulations in a slip-weakening model indicate that D_c can be estimated within an error of 50% as the slip displacement at the time of the peak slip-velocity T_pv from the near-field fault-parallel component of ground motion.  This technique may provide the only estimate of D_c independently of the fracture energy G, and therefore also an estimate of the strength drop using D_c and G.  The method provides a very simple approach that could lead to significant progress in characterizing the friction of earthquake rupture.

Burbank/Olsen

University of Southern California

075639-F

3D Ground Motion Simulation in Basins

02/01/02-01/31/07

$17,500

The project will foster the integration of 3D ground motion simulation methods and results into engineering applications.  We will validate 3D simulation methods and apply them to complex geological structures, with emphasis on urban sedimentary basins.  We propose a coordinated, multi-institutional investigation, with funding shared between the Pacific Earthquake Engineering (PEER) Center and the Southern California Earthquake Center (SCEC).  The PEER and SCEC research components will be fully integrated, and the project will be structured to address the engineering and science requirements of both Centers.  A companion proposal with the same title and team of investigators was submitted to SCEC in December 2001.

Burbank/Olsen

University of Southern California

075639-G

Fully Three-Dimensional, Multi-Scale Waveform Tomography for the Los Angeles Basin

02/01/02-01/31/07

$10,000

We propose to conduct a 3D tomography study for the seismic velocities in the LA Basin and its immediate neighboring regions.  The approach we take represents an improvement to the similar studies in three aspects.  First, we use waveform-based measurements such that more information in seismic records can be utilized to provide better constraints (coverage) to the velocity structure.  Second, we adopt accurate finite-difference method to compute sensitivity or Frechet kernels of the measurements so that 3D reference models can be accommodated without the need for high frequency or averaging approximations.  Finally, we pursue the inversions in a multi-scale fashion, starting from lower frequency and inverting for larger-scale structures, and progress to higher frequencies and smaller-scale structures.  This ensures that the linearity between data and structural parameters is better preserved at each step of the inversions.

Burbank/Olsen

University of Southern California

075639-H

How Can We Improve Ground Motion Estimates by Lessons Learned from Rupture Dynamics?

02/01/02-01/31/07

$25,000

The proposed research is a priority within several SCEC focus groups.  The Fault Systems Group asks for examination of the effects of fault (Goal 2f) and fault-zone (Goals 2a, g) complexities.  In the Rupture Dynamics Group, goals include rupture branching (Goal 4e), normal-stress effects (Goal 4f), and rupture behavior at step-overs (Goal 4h).  The Wave Propagation Group requests analysis of near-fault ground motion and the effects on strong ground motion from energy trapped between the fault plane and the free surface for thrust fault. (Goal 5-4).

 

Here, we propose to address these issues to improve estimates of strong ground motion using significant advances recently obtained in dynamic rupture modeling.  We will compare traditional prescribed (kinematic) and spontaneous dynamic rupture propagation and will report on differences for thrust faults with various dip angles and dynamic friction.  We will examine the significance of fault curvature and bends on near-fault strong ground motion.  Finally, we will examine to which extent broadband strong motion synthetics may be improved by including results from dynamic rupture modeling, such as the shape of the sliprate functions and variation in rise time.

Burbank/Oskin

University of Southern California

075639-I

Toward a Structural Representation of the Plieto Thrust System and the Architecture of Transpressive Fault Systems

02/01/02-01/31/07

$20,000

Geologic studies in the previous 10 years under the guidance of SCEC have significantly advanced our understanding of the structure and kinematics of the Pacific-North America plate boundary fault system in southern California (Working Group on California Earthquake Probabilities, 1995; SCEC group C., 2001).  Where significant discrepancies remain between geologic and geodetic strain estimates, these areas are often with the transpressive fault systems of the central and western Transverse Ranges where complex interactions occur between strike-slip and reverse fault systems.  This region has been the locus of considerable debate over the geometry of reverse faults (e.g. ‘thin-skinned’ or ‘thick-skinned’) and the interaction of strike-slip and reverse faults (e.g., Shaw and Suppe, 1996; Sneider et al., 1996).  These issues are central to resolving outstanding strain-rate discrepancies in southern California, such as compression across the Los Angeles basin (Walls et al., 1998) and strike-slip through San Gorgonio Pass (Spotilla and Sieh, 2000).  Resolution of these problems will have broad implications for the distribution of seismic hazard in southern California and for discerning the short-term and long-term behavior of fault networks.

Burbank/Oskin

University of Southern California

075639-J

What is the Relative Magnitude of Transient Loading of the Blackwater Fault?

02/01/02-01/31/07

$30,000

Does transient loading of faults occur, and can this process trigger earthquakes?  Past observations indicate systematic fault behavior consistent with transient stress triggering.  For example, sequential rupture of the North Anatolian fault in a series of six earthquakes over magnitude 7.0 from 1939-1967 suggests that each rupture loaded an adjacent fault segment (Ambraseys, 1970; Stein et al., 1997).  Postseismic relaxation following the magnitude 7.3 1992 Landers earthquake may have transiently loaded the adjacent nucleation point of the magnitude 7.1 1999 Hector Mine event (Pollitz and Sacks, in press).  Paleoseismic studies of the Eastern California Shear Zone also indicate earlier clusters of earthquakes here (Rockwell et al., 2000), supporting the concept of stress triggering as an important component of near-term seismic hazard.

Burbank/Sorlien

University of Southern California

075639-K

Building the SCEC 3D Community Fault Model:  Santa Barbara Channel and Santa Monica Bay

02/01/02-01/31/07

$30,000

We have produced digital structure-contour maps of deformed strata and of fault surfaces that cover a large area of Santa Monica Bay, Santa Barbara Channel, and offshore south-central California.  SCEC funds are requested for extending and completion of existing digital maps and for construction of a web page for release of these maps.  These maps and related information will be made available for use in the 3D Community Fault Model (CFM).  This effort also includes improving the velocity model and depth conversion for certain maps, and improving the gridding from digitized contours for others.  Mapped fault surfaces include the Red Mountain, North Channel, Pitas Point, and Dume (offshore Santa Monica).  SCEC funding will allow us to construct digital surfaces on the offshore Oak Ridge fault and on the offshore Malibu Coast-Santa Cruz Island fault, and extend mapping on the offshore Red Mountain and other faults.  We will have NEHRP funding during 2002 to complete mapping in northeast Santa Monica Bay, including the offshore Santa Monica-Dume fault, Palos Verdes fault (if present, Fisher et al., 2001), and on strands of the broad San Pedro basin fault zone.

Burbank/Steidl

University of Southern California

075639-L

SCEC Borehold Instrumentation Program

02/01/02-01/31/07

$25,000

One of the major goals of the Center is to compute theoretical seismograms for scenario earthquakes in the Los Angeles and Southern California region.  Existing strong-motion data are used to calibrate and improve our computational techniques.  Ground motions recorded at strong motion stations throughout Southern California are a combination of the complex earthquake source process, the propagation path from the source zone to the station, and the local near-surface site conditions at the station.  Separation of source, path, and site effects is limited by the current availability of data, the lack of detail in our knowledge of the crustal structure, and our understanding of the earthquake source process.  Widespread and varied ground motions and damage patterns over short distances produce a large degree of uncertainty in our ability to predict ground motion from future earthquakes.  In order to reduce the uncertainty in our theoretical seismograms of possible scenario earthquakes, we will observe and remove the near-surface site effect at a few select stations having ‘typical’ southern California soil profiles by using borehole instrumentation.  Observations from the SCEC borehole project allow for direct estimation of site effects, provide a test for the calibration and improvement of physical models of soil response, and give us a clearer picture of the incident ground motion that can then be used to study in more detail the earthquake source process and the regional crustal structure.

Burbank/Steidl

University of Southern California

075639-M

SCEC Portable Broadband Instrument Center

02/01/02-01/31/07

$40,000

The Portable Broadband Instrument Center’s (PBIC) ability to respond rapidly to a major Southern California earthquake with the deployment of seismographs in the near-source region is a critical asset of SCEC.  This has been highlighted by the success of the PBIC deployments from four major earthquake sequences in the past decade.  The ability to conduct innovative experiments using PBIC equipment in between earthquake sequences is another important asset of SCEC.  The list of PBIC publications is a testament to the importance and success of the SCEC PBIC program and how it has facilitated research over the years.  This proposal is to continue support of the operations and maintenance of the existing PBIC equipment, to continue the software and web development, and to serve as seed funding for a new state-of-the-art PBIC proposal that will be submitted to the NSF Major Research Instrumentation (MRI) program in January, 2003.  This new PBIC would include wireless communication technology and next generation network dataloggers for seamless integration of data into the Southern California TriNet regional network, or any other regional network that supports real-time telemetry of data.

Burbank/Tanimoto

University of Southern California

075639-N

Large-Scale 3D Crust and Upper Mantle Structure in Southern California from TriNet Broadband Data Set

02/01/02-01/31/07

$20,000

Taking advantage of a vast amount of broadband seismic data from TriNet, we propose to construct a model of 3D large-scale structure in Southern California.  Specific data to be analyzed are teleseismic surface waves and body waves recorded by TriNet.  The resulting structure will be of a lower resolution than the one developed by the Community Velocity Model but has two attractive features:

 

• S-wave velocity structure in the crust and mantle down to a depth about 100 km can be constrained.  The model will constrain large-scale features of 3D structure in the crust and mantle and thus may serve as a good starting model for the inversion of more detailed 3D structure. 

 

• The model provides a well-constrained overview of long-wavelength features in the entire Southern California.  It will help us understand the overall tectonic features.  Our preliminary maps contain some surprising features that may lead to new understanding of large-scale tectonics in this region.

 

We have collected phase velocity data from TriNet for about 3000-4000 paths for Rayleigh and Love wave data and are in the process of measuring body wave differential travel times for about 70 events we have collected so far.  During the proposed period of this study, we will develop a 3D S-wave velocity model for Southern California which will satisfy both surface waves and differential body wave travel times.  We will also examine existing P-wave velocity models (e.g., Kohler et al., 2001) by measuring P-wave differential travel times in TriNet data.

Burbank/Archuleta

University of Southern California

075639-A

Radiated Seismic Energy from a Dynamic Faulting Model of the Northridge Earthquake

02/01/02-01/31/07

$30,000

We propose to compute the seismic radiated energy for the 1994 Northridge earthquake.  First we will determine the initial stresses from the slip distribution using the method of Bouchon (1997).  From the stress distribution we will derive a spatially heterogeneous initial stress and yield stress.  The sliding friction stress will be fixed.  From this distribution of stresses and in concert with a slip weakening friction law we will dynamically rupture the fault.  The static stress drop will allow the computation of the elastostatic work available.  This work is partitioned into work spent during fracture (fracture energy and relaxation) and work radiated as seismic energy.  We will compute the radiated seismic energy as we have done for the 1979 Imperial Valley earthquake.

Burbank

Department of Interior

03HQGR0051

Rates of Vertical Deformation Above Blind and Poorly Exposed Faults:  Developing

01/01/03-12/31/03

$50,000

Although blind thrust faults create major seismic hazards in southern California, paleoseismic assessment of these hazards has been hampered by the inaccessibility of faulted deposits.  Despite the “hidden” nature of these faults, rock-uplift rates of their hanging walls can provide a valuable proxy for slip rates at Holocene and longer time scales along the causative faults.  An ability to define spatial variations in geologic slip rates along individual faults and between suites of regional faults will serve to identify the most actively deforming blind thrusts, will help to resolve discrepancies between geodetic and paleoseismic deformation rates, and will aid in identifying and quantifying the seismic hazard resulting from blind faults.  We propose to develop, calibrate, and test a new quantitative geomorphic “tool,” specifically, a river channel-incision model that utilizes measures of gradients, channel concavity, and steepness to define long-term rock-uplift rates.  In non-glacial landscapes, the equilibrium channel gradient (S_e) decreases as a power function of drainage area according to the relation:

;  where     and ;

where k_s and q are the steepness and concavity indices, respectively; U/K is the ratio of rock-uplift rate to the erosion coefficient; and m and n are the exponents on discharge and channel slope in the standard stream-power  law.  These parameters are extracted from digital elevation models (DEMs), and, consequently, they have wide applicability and are readily defined. Preliminary testing of this incision model on folds in the Himalayan foreland has yielded striking results that faithfully reproduce measured variations in Holocene deformation rates.  Given the increasing availability of high-resolution DEMs, a readily applied analytical “tool” that defines uplift rates would yield critical insights on the deformation patterns and rates of these hidden, but clearly seismogenic faults.  We request a year of support to extensively test and calibrate this channel-incision model in coastal southern California.  We will utilize test domains characterized by well defined variations in rock uplift, lithology, base-level, and DEM resolution in order to assess the potential impact of each of these parameters on channel characteristics. Our goal is to test the limits and robustness of the model and to define those situations in which it can be most reliably applied.  Following our calibration, we will apply our model to several test sites in the Los Angeles basin.  If successfully developed and calibrated, this channel-incision model will provide a valuable tool for rapidly assessing rock-uplift rates associated with both blind and emergent dip-slip faults wherever DEMs with adequate resolution are available.  Ultimately, in addition to its direct application to blind thrust faults, such an analytical approach would be useful in extensional provinces, such as the Basin and Range, as well as anywhere that differential rock uplift creates significant topographic gradients. First, however, it needs to be extensively tested.  We propose to do that over the coming year.

 

Burbank

National Science Foundation

EAR-0196414

Collaborative Research:  Geomorphic-Geodynamic Coupling at the Orogen Scale:  Himilayan Transec in Central Nepal

03/15/01-09/30/04

$1,110,318

One of the most provocative-yet largely untested-recent hypotheses concerning orogenic evolution is that regional variations in climate strongly influence spatial variations in the style and magnitude of deformation across an actively deforming orogen.  Recent progress in quantifying rates of both tectonic and geomorphic processes and in modeling surface and lithospheric processes sets the stage for an integrated, quantitative, field- and model-based investigation of the interactions and feedbacks between geomorphic, climatic, and tectonic processes.  We propose to examine these interactions where they are likely to be most clearly expressed:  the Nepalese Himalaya.  Not only in this the quintessential collisional orogenic belt, but its topographic growth and erosional history have been suggested as key controls on global climatic changes.  Our integrated study focuses on a major transverse catchment, stretching from the edge of the Tibetan Plateau to the foreland and traversing some of the highest topography in the world.  This transect spans the major structural elements of the Himalaya, as well as monsoon-to-rainshadow climatic conditions.  We bring together expertise in process-based geomorphology, glaciology, climatology, structural geology, thermochronology, cosmogenic radionuclide dating, modeling, and documentary film making for a multi-pronged approach intended to evaluate one overarching, but largely untested hypothesis:

 

• Rates of erosion vary spatially as a function of climate and this spatial variability in erosion controls the partitioning of deformation within an orogen.

 

Furthermore, we will collect data to assess the following related, but subsidiary hypotheses:

• The erosional response to rapid lateral advection of crust across a basement ramp-crustal scale fault-bend folding, for example-creates erosion rates that are nearly equal across the entire topographic escarpment of the Himalaya, ranging from 8 km to 1 km in elevation.
• Above a certain threshold erosion rate, the topography attains a dynamic ‘equilibrium’ or steady state that is independent of erosion rate.
• Topographic characteristics (relief, slope angles, normalized river gradients) correlate more strongly with erosion rates than they do with variations in climate or lithology.

 

Despite the broad scope of these hypotheses and the impossibility of resolving all details, we have developed a research strategy that, over a four-year span, will enable us to define the primary characteristics of denudation, rock uplift, climate, and topography across the Himalaya and to calibrate some process-based ‘rules’ for major erosional agents, such as glaciers, rivers, and landslides.  A key to success will be the integration of data from diverse subdisciplines (climate, geomorphology, tectonics) at the scale both of intensively monitored subcatchments and of the entire trans-Himalayan catchment.  Spanning seven subdisciplines in earth and atmospheric sciences, this project brings together researchers from seven US institutions and three governmental agencies in Nepal.

Busby

Department of Interior

03HQAG0030

Geologic Mapping of Tertiary Volcaniclastic  Rocks in the Northern Sierra Nevada

04/21/03-04/20/04

$31,400

Volcanic and volcaniclastic rocks of the northern and central Sierra Nevada (California) represent a piece of the Neogene volcano-tectonic puzzle about which very little is known, relative to the rest of the western United States.  This is a really extensive "missing piece" of the Neogene volcano tectonic puzzle is an important piece, because it lies in a tectonic setting that is transitional between subduction, Basin and Range, and hotspot settings (Dickinson, 1997).  These rocks are also important because they may provide clues about the relative and absolute elevations of the Sierra Nevada and adjacent Basin and Range province through time, as well as the timing of their differentiation, and the amount of strike slip faulting between them (Cashman and Fontaine, 2000; Henry and Perkins, 2001).  Through a combination of existing NSF and proposed EDMAP funding, I will be able to build a team of graduate students working together to attack these problems on several fronts.  They can thus learn from each other, as well as from me and my collaborators.

 

The biggest societal impact of the proposed projects lies in understanding the active range-front normal faults of the Sierra Nevada, as well as active strike slip faults of the Walker Lane.  Another societal impact for the projects south of Lake Tahoe is that they involve areas that are virtually unmapped geologically, even though they are heavily used for recreational purposes.  We will make our new maps available to the U.S. Forest Service for dissemination to the public.

 

Another major societal impact of this project is the development of new mapping technologies.  One of the main goals of the research is to understand the paleotopographic evolution of the Sierra, by mapping paleocanyons of various ages and determining how the various faults grew through time.  This work will integrate classic geologic mapping techniques with new technology.  Using ARC GIS, my students will integrate field map and GPS data points with the USGS Digital Elevation Models and the DOQQs for all of the proposed field areas.  Our three-dimensional data set will be displayed in digital publications using a program such as Autocad or ENVI.  Each student will present his results as a video animation “poster” at the Fall 2003 AGU meeting.  I am involved in the governance of an international geological society (Society for Sedimentary geology) and I know that all of the international geological societies are switching to online journal publication with links to digital 3D data displays (including animations).  My students will be in the first wave of this technology.

Clark

University of California Institute of Geophysics & Planetary Physics

03-GS-024

Imaging Time Scales of Flow and Transport within the Mission Tunnel Fracture

10/01/02-09/30/03

$32,000

Understanding flow and transport within fractured rock systems is important for developing cost effective management strategies for controlling contaminant plumes and potable water supplies in many important localities including potential radioactive storage sites.  Assessment of fracture rock systems is often limited by the available field data.  The historical record (25 yr) of bedrock discharge into the tunnel, its relatively simply geology, and the numerous seeps that can be sampled, makes the Mission Tunnel flow system an ideal location to study the response of flow and transport to variations in recharge in a fractured rock system.  Additionally, recharge to the system during water years 2002 and 2003 should be significantly different.  Recharge during 2002 will be relatively small given the current drought and it should be unusually large next year as the result of the expected El Niño conditions.  The proposed work includes collecting weekly bedrock discharge data and collecting samples from five seeps within the tunnel during April 2002 and 2003 for analyses of tritium, radiocarbon, and other geochemical data.  The latter data will be used to estimate transport times.

Clark

University of California Los Alamos National Laboratory

10010

CULAR Insight into Gulf Stream Changes During the Last Glacial Period

10/01/02-09/30/03

$64,041

We are proposing (1) to use noble gas paleo-thermometry to determine the glacial temperature and stable isotopic composition of ocean water archived in the Floridan aquifer and (2) to modify the microwave source method of Poths and Chamberlin (1995) to provide a new rapid, high accuracy system for noble gas analysis in groundwater samples. Combining paleotemperatures with direct measurements of salinity (determined from conductivity) will allow us to calculate the density of the glacial ocean water at the bottom of the Floridan Straits.  Furthermore, we will measure the stable isotopic composition of this water to determine the glacial/Holocene change in this important paleoceanographic parameter and major ion chemistry so that mass balance calculations can be made to estimate dolomitization rates. 

 

Recently, using proxy data from foraminifera to calculate paleo-density profiles, Lynch-Stieglitz et al. (1999a) determined that the glacial Gulf Stream was significantly weaker (50%).  This result supports the hypothesis that changes in ocean circulation cause abrupt climate change.  Their calculation is based on the conversion of the d18O composition of benthic foraminifera to the density of seawater.  Using foraminifera data collected on either side of the Floridan Strait during both the Holocene and glacial, these authors were able to calculate the density gradient through the Gulf Stream and, hence, to calculate its geostrophic flow.

 

Foraminifera data has rarely been used to calculate density because the d18O composition of foraminifera is a function of both water temperature and the seawater d18O composition, which is in turn a function of salinity and ice volume.  Using their innovative approach, Lynch-Stieglitz et al. (1999a, 1999b) developed an empirical relationship between density and foraminifera d18O composition for the modern ocean using GEOSECS data from the western Atlantic.  To determine this relationship during the glacial, they assumed a change in the ocean's salinity and d18O composition of 1 salinity unit and 1‰ (Schrag et al., 1996; Mashositta et al., 1999), respectively, due to the build-up of continental ice.  Furthermore, they assumed that the salinity-d18O relationship of seawater results from mixing between sub-thermocline ocean water (with a composition equal to the mean ocean value) and high latitude continental run-off.  The latter end member they assumed decreased by 4‰ during the last glacial period.  The proposed work will provide important independent data of the deep water composition and density in the Floridan Straits during the glacial period (i.e., d18O, temperature, and salinity) so that the results of Lynch-Stieglitz et al. (1999a) can be critically evaluated.

Gans

National Science Foundation

0230439

Neogene Evolution of the Sonoral Margin:  The Transition from Backarc Extension

01/01/03-12/31/03

$360,347

Many of the fundamental processes that govern continental rifting and lead to rupturing of continental lithosphere and birth of an ocean remain poorly understood.  The transtensional Gulf of California - Salton Trough represents a superb natural laboratory to explore these issues.  It provides along-strike and across-strike views of the rifting process and records the transition from distributed continental extension in a backarc setting to final rupturing of the North American lithosphere and capture of Baja California by the Pacific Plate along the modern transform margin.  Though much progress has been made in understanding the plate tectonic framework and modern strain field of this region, how this continental rift system evolved in space and time is still poorly understood.  Our limited knowledge of how extensional and transcurrent strains are spatially and temporally distributed on the adjacent continental margins - particularly the Sonoran Margin, has made it difficult to adequately evaluate and test models for the kinematic and dynamic evolution of this rift.

 

This proposal requests funds to quantify the distribution, magnitude, timing, and style of Neogene deformation and magmatism across a portion of the Sonoran rifted margin in order to evaluate the kinematics of the transition from earlier (pre-12 Ma) distributed backarc extension to post-12 Ma transtensional deformation associated with the cessation of subduction and transfer of Baja California to the Pacific Plate.  This is an ambitious multi-disciplinary study that will bring together scientists and students from the U.S. and Mexico in an attempt to unravel the history of extension and strike-slip faulting within a particularly well exposed but poorly understood  rifted continental margin adjacent to the Gulf of California.

 

The principal tool to be employed is geologic mapping, as this is the only way to identify the important fault systems and to work out the details of local structural, volcanic, and sedimentary histories.  Six investigators (3 senior personnel and 3 Ph.D. students) will devote up to two months/year in the field over a three year period with the goal of deciphering in detail the structural evolution of a 80 by 100 km area in southwestern Sonora, from the coast near Guaymas to the Sierra Mazatan metamorphic core east of Hermosillo.  In addition, structural and stratigraphic studies will be carried out on two representative Neogene basins in eastern Sonora to assess whether significant late Miocene deformation affected areas further inboard.  Approximately 60 new high-precision 40Ar/39Ar age determinations on key pre-, syn-, and post-tectonic volcanic units will be obtained to document local volcanic and sedimentation histories and to bracket the timing of structural events.  K-feldspar 40Ar/39Ar multi-domain diffusion, apatite (U-Th)/He, and fission track analyses will be employed to determine low temperature cooling histories in the footwalls of large normal fault systems to assess extensional slip histories and to gain insight into erosion rates and thermal structure of the upper crust in the past.  This evolving structural, stratigraphic, and geochronologic database will be compiled and continuously updated in a GIS format and made available to the geologic community via the web.  Some of the important questions to be addressed by our study include:

·How is strain distributed across the Sonora rifted margin?  What are the magnitudes of extension and transform motions across this margin (a) prior to the cessation of subduction at this latitude (pre 12 Ma), (b) during early (12-6 Ma) transtensional deformation, and (c) after final rupturing of the lithosphere and opening of the Gulf of California (post 6 Ma).

·Do the observed strains magnitudes and strain histories on the Sonoran margin support the kinematic model of Stock and Hodges (1989), wherein Pacific-North America plate motions were initially partitioned between orthogonal extension inboard of Baja and strike slip deformation outboard of Baja California during "Proto-Gulf" transtensional deformation?  Or do the observed strain histories on the Sonora margin suggest an earlier or more gradual transfer of Baja California to the Pacific Plate?

·Was the earlier backarc and intra-arc extension(e.g. Gans, 1997) continuous in space and time with younger (post 12 Ma) deformation associated with the change to a transform margin?  What influence did the older extensional deformation have on the geometry and kinematics of the younger extensional and/or strike-slip deformation and are their fundamental differences in structural style and strain rate between the deformations that occurred in these two fundamentally different tectonic settings?

·Where was the locus of volcanism during the Neogene evolution of the Sonoran margin and how did its character change as the plate margin evolved from convergent to transform?  What is the spatial and temporal relationship between Neogene magmatic activity and deformation? 

·What was the character and timing of Neogene sedimentation on the Sonoran rifted margin (as recorded by widespread lacustrine and alluvial fan deposits) and how does this sedimentation relate to the structural evolution? 

·Fundamentally, how does the deformational history of the Sonoran rifted margin relate to the geometry and kinematics of the evolving North America-Pacific plate boundary and what does this imply about the relative importance of plate boundary versus body forces as a driving mechanism for distributed continental deformation?

The greatly improved understanding of the Neogene pre-rupturing history of the Gulf of California region that will emerge as a direct consequence of our investigation of the Sonoran margin will place critical new constraints on models for the evolution of this continental rift.

Gans

Rio Tinto America Industrial Minerals

SB030073

Structural and Stratigraphic Setting of Borate Mineralization in the Eastern Rio Tinto

01/01/03-06/30/04

$32,099

Funds are requested to support an integrated field and geochronologic investigation of the eastern Calico Mountains with the aim of understanding the structural and stratigraphic setting of borate mineralization in the Old Borax deposit.  This study will constitute the Masters Thesis research project for John Singleton, under the direction of Dr. Phil Gans at UCSB.  The study will include:

(a)   Detailed geologic mapping at a scale of ~ 1:10,000 of a ~7 square mile area in the eastern Calico Mountains, including the Old Borate deposit.

(b)  Construction of restorable cross sections across the eastern Calico Mountains, illustrating the map scale structure and stratigraphy of this area.

(c)   Construction of detailed stratigraphic columns of the Miocene sedimentary and volcanic section for different parts of the eastern Calico Mountains, illustrating variations in the character and thickness of different lithologic units.

(d)  Detailed structural analysis of map and outcrop scale faults and folds in the eastern Calico Mountains, with a description of the geometry of various structures and an assessment of the sequence and kinematics of structural events.  Specifically, structural data will be collected to document the deformational history of this region and to evaluate how much of this deformation is a consequence of extension and normal faulting vs. gravity sliding, vs. transpression or regional contraction.

(e)   ⁴⁰Ar/³⁹Ar geochronology on any dateable units within the sedimentary and volcanic section that will better constrain the timing of sedimentation, volcanism, mineralization, and structural events in the range.

 

This evolving data base will be made continuously available to US Borax personnel as the study proceeds, and copies of the final masters thesis and any supplementary data will be provided to interested parties upon completion of the study by June of 2004.

Gans

University of California Mexus

SB030019

Timing and Magnitude of Extensional Deformation in the Sierra Mazatan

07/01/02-06/30/04

$11,990

Metamorphic core complexes exposed in Sonora cover vast areas (Nourse et al., 1994) and each one is likely complex enough to justify an individual dissertation.  This study will focus on understanding the extensional history and evolution of the Sierra Mazatan metamorphic core complex, located 70 km east of Hermosillo.  Sierra Mazatan is the southern-most recognized core complex in Sonora and most clearly lies within the area affected by rift-related extension in the Gulf as defined by Stock and Hodges (1989).

 

The objectives of this study are twofold:  (1) determine the magnitude of extensional deformation in the Sierra Mazatan core complex, and (2) determine the precise timing of the inception and duration of this deformation.  These data will provide new information on how and when extensional deformation occurred within the rifted margin as a whole.

Gans

University of California Mexus

SB030020

Neogene Sedimentary Basin Development in East-Central Sonora, Mexico

07/01/02-06/30/04

$11,998

The region of east central Sonora, Mexico, is part of the southern Basin and Range province as well as the eastern extent of the Gulf of California extensional corridor.  Neogene continental basins in the region contain variably tilted sequences of conglomerate, sandstone, and basalt flows.  Sedimentary basins are important surface expressions of continental rifting and extension; sediment characteristics and depositional environment are directly affected by local and regional tectonic activity.  In addition, basin analysis can provide direct constraints on the local timing, magnitude, and the architecture of rifting, especially when datable volcanic deposits are interbedded with sedimentary units.  Preliminary fieldwork has been started in the Sahuaripa basin and this project proposes to expand the study to basins west of Sahuaripa including the Rio Yaqui basin.  Previous workers have determined ages for some of the volcanic deposits in basins to the south and west of the proposed study area indicating that most of the basins began to develop by the mid-Miocene.  Detailed structural and lithologic mapping, stratigraphic, sedimentologic, and 40 Ar/39 Ar geochronology analysis of the sequences as well as the Mesozoic basement of the area will provide data with which to reconstruct the geologic history of the basins as well as comparison of seemingly similar adjacent basins.

Hacker

National Science Foundation

EAR-0215641

Collaborative Research:  Thermal, Petrological, and Seismological Study of Subduction Zones

09/01/02-08/31/04

$130,126

We propose to continue our thermal–petrological­–seismological study of subduction zones to attack some significant new issues:

1) The geometry and vigor of mantle-wedge convection represent a major source of uncertainty in modeling the thermal structure of subduction zones.  To better understand the extent of hydration and the relationship between forearc mantle hydration and the depth of slab–wedge viscous coupling, we propose to ...

2) Expanding our phase diagrams—and hence automated rock properties calculations to metasomatized MORB will address how the variability of oceanic crust affects physical properties, dehydration, and, potentially, seismicity.  We will incorporate the effects of fluid or melt-filled cracks or other porosity into our calculations, and deliver this improved mineral and rock properties spreadsheet to the community.

3) Further tests of the dehydration–seismicity hypothesis will be made by examining the petrological structure–seismicity patterns in more subduction zones—especially those with PT paths intermediate between the “hot” and “cold” endmembers—and by evaluating whether along-trench changes in seismicity along individual subduction zones vary in ways consistent with the dehydration–seismicity hypothesis. We will also determine whether peaks in seismicity and moment rate correlate better with areas of predicted dehydration or to changes in slab shape.

4) Testing the hypothesis that lower seismic zones are permitted by mantle dehydration...

5) Using full-waveform modeling coupled with the petrologic modeling, we will test a suite of realistic slab models against the observed dispersion curves.

6) Earthquake hypocenters provide key tests of the double seismic zone hypothesis, the hypothesis that the main zone is associated with hydrated mafic rock, and the notion that the forearc mantle wedge is aseismic.  Specifically, it would be valuable to place constraints on the maximum/minimum possible width of a double seismic zone, on locations of dip changes, and to quantify the likelihood of any possible events lying within the mantle wedge.

Hacker

National Science Foundation

EAR-0003568

Collaborative Research:  United States-China Scientific Cooperative Project

08/01/01-07/31/04

$135,479

The Sulu ultrahigh-pressure (UHP) metamorphic terrane in east-central China is part of the Sulu-Dabie-Hong’an-Qinling suture between the Sino-Korean and Yangtze cratons.  Together the Sulu, Dabie and Hong’an terranes constitute the world's most extensive exposures of UHP rocks and have been identified as the primary Chinese research target for the next five years.  We propose a multidisciplinary investigation of the Sulu UHP terrane in conjunction with the Chinese Continental Scientific Drilling Program (CCSD).  Our objective is to understand the mechanisms and processes by which buoyant continental crust is subducted to depths exceeding 100 km and then exhumed, and to quantify the relationships of this process to continental collision.  Reflection seismic profiling, structural geology, rare-earth-element geochemistry, geochronology, stable- and radiogenic isotope geochemistry, petrology and mineralogy—of surface rocks and core samples from the CCSD project—will be employed to test existing geodynamic hypotheses. We plan to build on our 10-year geochronological-petrological-structural study of the Dabie-Hong’an area by completing a parallel study in the Sulu region.  Validated models of UHP tectonics and continental collision will be built upon the foundations provided by this and previous work.

 

It is an accepted tenet of geology that very low T at high P constitutes a “forbidden zone” never realized in the Earth— all exposed rocks appear to have experienced geothermal gradients hotter than 5–10°C/km. In the Sulu-Dabie terrane, however, we have recently discovered ultramafic rocks from the forbidden zone.  These rocks must have formed in a cold subduction zone and constitute important recyclers of H2O into the mantle.  Recent UHP experiments reveal that numerous hydrous phases are stable in the forbidden zone; some occur in the Chinese UHP rocks.  Garnet peridotites with an upper mantle signature are rather abundant in the Sulu region and are a major target of the CCSD project.  They provide not only a wealth of information on the physical and chemical characteristics of the lithospheric mantle, but also provide valuable insight into the dynamics of crust/mantle interaction during continental subduction, during collisional orogenesis, and within the forbidden zone.

 

The key questions we expect to answer are:

(1) What crust-mantle interaction processes take place when continental material is subducted to great depths, and how do such processes affect crustal growth and global geochemical recycling? Can state-of-the-art analytical tools determine the age of fluid/rock interactions?

(2) What new constraints on petrotectonic processes do UHP garnet peridotites of the mantle wedge provide? How were such peridotites emplaced into the crust during subduction, and how did they evolve during exhumation?

(3) What are the implications of UHP metamorphism at forbidden-zone P-T conditions and what roles do hydrous phases in the cold subducting slab play in the recycling of volatiles into the Earth’s mantle?

(4) How do we differentiate the subduction/collisional architecture of orogens from the effects of younger events using present-day deep-seismic profiles?

(5) What exhumation mechanisms and rates of ascent prevent UHP mineral assemblages from being completely obliterated by metamorphic overprinting and/or partial melting?

(6) In what tectonic settings are the generation and exhumation of UHP rocks possible? Is continental collision required?

 

Our proposed U.S.-China–Japan–France–Germany–UK cooperative project will establish fruitful scientific exchange among international researchers.  We will obtain essential seismic, structural, petrochemical, mineralogical, and geochronological data that address the questions enumerated above.  It is important that this project begin soon to take advantage of the ICDP Donghai drilling project started in 2000.  We have already begun exchanges with our CAGS colleagues, and limited research on core samples recovered from the pre-pilot holes has commenced.

Hacker

Woods Hole Oceanographic Institution

A100169

Contraints on the Genesis of Continental Crust via Arc Magmatism:  Geology

08/01/00-07/31/03

$259,576

This proposal is for a multi-year, interdisciplinary study of the exposed crustal section of the Talkeetna island arc to address the rate and mechanism of continental growth at convergent margins. The Talkeetna arc section, particularly in the Nelchina-Tonsina region, is a crustal section through an accreted, Jurassic subduction-related magmatic arc, from volcanic, volcaniclastic and sedimentary rocks at the top to residual mantle peridotites at the base.  Detailed studies of exposed, island arc sections can provide a crucial link between geophysical observations and geochemical studies of volcanic rocks in active arcs.  In the same way that ophiolite studies have provided an ideal counterpoint to both marine geophysics and analysis of mid-ocean ridge basalts in developing a complete picture of crustal accretion at oceanic spreading ridges, studies of arc sections will be essential to progress in understanding arc magmatism and crustal genesis over the coming decade.

Our study addresses a key question regarding arc processes:  What is the rate and mechanism of continental growth at convergent margins?  Arc crust is basaltic.  Continental crust is formed mainly in arcs.  Continental crust is andesitic.  How can these three ideas be reconciled?  Clearly, although each of these points is open to question, research funded by this grant will mainly address the first one. However, in our proposed study we will also determine compositional layering of the arc crust, and constrain proposed scenarios for lower crustal delamination during and after arc magmatism.  Most importantly, work on the Talkeetna section can provide crucial constraints on the composition and timing of accretion of the middle and lower arc crust, which are generally not exposed in active arcs.  Evidence from rare plutonic exposures in the Aleutian and Izu Bonin arcs indicates that different processes or different primary magmas may produce intrusive and extrusive rocks, so that inversion of volcanic rock compositions is not sufficient to determine the bulk crustal composition, nor the nature of primary melts passing from the mantle into the lower crust.

In our proposed study, we will address various aspects of crustal genesis in a practical way, applying a variety of analytical techniques.  Our research goals are to (1) make an improved geological map and use a fully two -dimensional approach to better constrain the relative proportions of the different rock types in the Talkeetna arc crustal section; (2) determine the deformation history of lower crustal rocks, identify and date faults along which section may be missing or repeated, , make thermobarometric estimates from mineral compositions, and thereby better constrain how much of the section is missing and how to interpolate the data for the rocks that are exposed; (3) make extensive measurements of physical properties of rock samples for comparison with the growing database on seismic refraction and reflection in arcs; (4) conduct detailed investigations of residual mantle harzburgites and igneous ultramafic rocks just below the base of the gabbroic crust in order to determine the mode of melt transport from the mantle into the crust, and determine the relative importance of ultramafic “cumulates”; (5) conduct major trace and isotopic analysis on a comprehensive suite of samples from all the igneous rocks in the section, together with extensive new geochronology studies, to delineate how many liquid lines of descent are represented in the arc crustal section, and which are most volumetrically important; (6) use petrological and trace element modeling techniques to quantify the possible proportions of different rock types, for comparison with the proportions of rock compositions determined by geologic mapping, providing a further constraint on the bulk composition of the arc crust; and (7) to look at the P-T-t history of the lower crust, in order to constrain Moho temperatures in active arcs, and to provide constraints on the density and viscosity of arc lower crust during and after magmatism.

Kneller

British Gas PLC

SB030076

Three Dimensional Heterogeneity of Submarine Channel-Levee Systems:  Lithofacies

01/01/03-12/31/04

$44,000

Interpretation of channel systems and mass transport complexes in seismic data from the Gulf of Mexico.

 

The principal objective of the contract is to develop a long-term mutually beneficial relationship with the PI.  In the process, we may be creating a center of excellence in sediment gravity flow process understanding at Santa Barbara.  An additional objective is to enable individuals from BHPBilliton to join the PI at Santa Barbara, or in the field.  This should be of benefit to both BHPBilliton and the research program.

 

The PI will share the results from the first year of two consortium studies starting 2001 at Santa Barbara as described separately.  BHPBilliton will provide access to at least one of the 3D seismic surveys in the Western Atwater Fold Belt of the Gulf of Mexico, and the PI will provide a full description of the Plio-Pleistocene depositional system architectural elements (geometry, scale and internal structure) and post-depositional modification by gravity failure (geometry, scale).  The above should be integrated into a geological model.  To facilitate this work, the PI will spend six weeks in BHPBilliton’s offices in Houston during the calendar year 2002.  In addition, he will join BHPBilliton on a 10 day field workshop to the Karoo, South Africa. 

Kneller

University of Leeds

SB020081

Turbidites Research-Continuation

08/01/02-07/31/03

$215,824

In collaboration with Dr. W. D. McCaffrey at Leeds University on Phase 3 of the Turbidites Research Industrial Consortium I will conduct investigations into the properties and deposits of turbidity currents, and the applications of these studies to hydrocarbon reservoir prediction in the subsurface.

 

Luyendyk

University of California Energy Institute

SB030067

Volatilization and Dispersion of Marine Oil Slick

07/01/02-06/30/04

$35,020

The fate of oil in the marine environment is of interest to scientists, regulatory agencies, and industry. Natural oil seepage has been long used for prospecting, while mitigating and successful remediation of accidental oil spills is an important concern.  Decisions regarding potential resource exploitation and routing of shipping lanes requires informed decisions by resource planners from state, federal and local agencies.  We propose studying the evolution of oil slicks using the natural laboratory provided by the perennial marine oil slicks originating in the Coal Oil Point Seep Field in the northern Santa Barbara Channel.  At the ocean surface, the oil forms a slick and drifts under the effects of wind and currents. Volatilization of lighter oil components rapidly causes the oil's spectrum to shift towards higher molecular weight components.  The slick also evolves due to dispersion.  Using a catamaran drum oil sampler, drift buoys, and glass microspheres as surface tracers, the time evolution of the oil will be measured. Measurements will be used to improve current slick models, and thus aid in predicting how long after an oil spill sufficient volatile components remain for burning, which is the preferred and least environmentally harmful cleanup method.

Luyendyk

National Science Foundation

OPP-0088143

Collaborative Research:  Antarctic Cretaceous-Cenozoic Climate, Glaciation

09/15/01-08/31/04

$430,855

The Ross Embayment, including the Ross Sea rift, separates East and West Antarctica today.  The Ross Sea rift and western Marie Byrd Land (wMBL) are part of the West Antarctic rift system.  It is widely accepted that this region is undergoing active deformation, but the rates and causes of deformation are essentially unknown.  Crustal motions may be occurring across the Ross Sea rift today. Crustal uplift could be occurring in wMBL due to isostatic rebound following the last glacial age.  If tectonic motion is occurring in the Embayment this could greatly influence global plate circuit calculations.  Post glacial rebound in wMBL would depend on the configuration of the ice sheet during the Last Glacial Maximum and when this occurred.  The main question is whether or not the ice sheet collapsed in mid-Holocene time.

 

In December 1998 we installed three continuous and autonomous GPS stations on outcrops in wMBL, in the Rockefeller, Phillips, and Clark Mountains.  Results from three years of data collection indicate essentially no extension between McMurdo station (MBL4) and the network.  The results show an overall length rate of –0.7±3.5 mm/yr between MCM4 and the wMBL network.  With additional years of measurements we should be able to discriminate whether this rate is near zero or not to about 1 mm/yr.  We also expect to detect strain gradients within wMBL.  The network also suggests a dome of uplift centered near the Rockefeller Mountains, with the maximum rate being in the Rockefeller Mountains of 12±8 mm/yr.  This is consistent with proposed post-glacial rebound for the region.  With over seven years of data we expect to determine crustal strain rates to an accuracy of one mm/yr horizontal and 2 mm/yr vertical.  The strain data from wMBL and the Transantarctic Mountains will enable us to construct models for tectonic extension and glacial rebound in the West Antarctic rift.

 

We propose to continue operation of the three stations in wMBL for another four year period.  These stations will be upgraded with modern receivers and satellite data downloading when such downloading becomes feasible.  We will add an additional continuous station during the 2002/2003 season in the Transantarctic Mountains near the South Pole on Mount Howe.  We will install a second new continuous station at Mount Coates in the Transantarctic Mountains 2003/2004 season at the location of the previously operational continuous station. This will create a network that is geometrically ideal for understanding the orientation of maximum extension across the Ross Embayment and will clarify the pattern of postglacial rebound.  Should Mount Coates be re-established by Carol Raymond we will install that station at another location in the Transantarctic Mountains.

 

This project is collaborative with other geodetic investigations in Antarctica and we will freely share our data.  This includes networks led by Carol Raymond of JPL-Caltech in the Transantarctic Mountains, the WAGN (Marie Byrd Land) project led by Ian Dalziel, at University of Texas at Austin, and the Transantarctic GPS project led by Larry Hothem of the USGS.  We will also collaborate with Erik Ivins at JPL, who is an expert on postglacial rebound.  Our team brings together experts in wMBL geology and tectonics, tectonic geodesy, and lithospheric deformation.

Newell

National Science Foundation

EAR-0208446

Magnetic Hysteresis in Magnetite:  Are Synthetic Samples Stressed?

07/01/02-06/30/04

$63,613

Measurements of the magnetic properties of rocks can provide information on properties of

magnetic minerals that react environmental changes and affect the reliability of paleointensity

methods.  Recent technology allows us to measure magnetic hysteresis rapidly and represent

the full complexity of it using phenomenological models such as Preisach or FORC diagrams.

To interpret these diagrams, we need a good physical model for the magnetic particles.  I have

two goals in this proposal: to develop a quantitative model for hysteresis in some well characterized

synthetic magnetite samples, and to test it rigorously using hysteresis measurements

at several temperatures combined with detailed particle size distributions.  Recent micromagnetic

models for the size dependence of hysteresis are much closer than previous models, but

their predictions are still somewhat low.  The reason for this may be that they have neglected

an important source of magnetic anisotropy.  Estimates based on magnetic field cycling, low

temperature cycling, and other measurements on very fine magnetite particles indicate that

the anisotropy is much larger than usually supposed. I will test the hypothesis that stress

anisotropy has an important effect on hysteresis even in the smallest particles.

To calculate the magnetic hysteresis I will use a numerical micromagnetic model.  Over

the past few years I have been developing methods to increase the reliability of micromagnetic

calculations, and I will describe some new methods to estimate the errors in the calculations.

Because magnetic properties depend strongly on the method of synthesis, I will concentrate

on two sets of samples, aqueous precipitates and glass ceramics, with sizes below 0.4 microns.

These samples have been intensively studied, are small enough for accurate micromagnetic

modeling, and are analogues of natural systems.  I will assume the stress anisotropy is due

to lattice defects in the aqueous precipitates and thermal coefficient mismatch in the glass

ceramics.  To test the theory, I will make explicit use of measured size distributions and

use statistical tests to determine error bounds on facets of the model to the data.  I expect to

either produce a realistic model for the magnetic properties or eliminate some models from

consideration.  A successful model could be used to interpret Preisach and FORC diagrams. It

would also be the basis for future work on other magnetic phenomena such as thermoremanent

magnetization.

Newell

National Aeronautics & Space Administration

NAG5-13465

Quantification of the Evolutionary Forces Shaping Biogenic Magnetic and Criteria

05/01/03-04/30/06

$54,512

One of the goals of the Exobiology Program is to learn more about the early evolution

of life from the geological record in rocks.  I propose to develop quantitative criteria for

detecting fossil magnetotactic bacteria on Earth and elsewhere.  The methods I will use will

also improve our understanding of the evolutionary forces working on these bacteria, thus

addressing another goal of the Exobiology Program.

 

In the last few years, the evidence for life in the Archean has come under increased

scrutiny, and it has proved controversial.  For example, Schopf and Packer [1987] interpreted

¯laments in black cherts from the 3.5 Ga Warawoona Group of Australia as fossil cyanobac-

teria, and these have long been considered the oldest known fossils.  However, Brasier et al.

[2002] has recently argued that they are just carbonaceous blobs, the result of scalding water

acting on the surrounding sediments.  Another line of evidence for Archean life is isotopic

depletion of graphite inclusions in apatite crystals from 3.8 Ga banded iron formations in

Greenland [Mojzsis et al., 1996].  The date has been challenged by Sano et al. [1999], who

argue that the apatite is around 1.5 Ga. Even Archean stromatolites may be abiogenic

[Grotzinger and Knoll, 1999].  Whether or not the challenges stand [e.g., Mojzsis et al., 1999,

Schopf et al., 2002], it is clear that the standard is getting higher for biomarkers on Earth.

One of the primary goals of missions to Mars in the next few decades will be to look

for signs of life, most likely the fossil remains of unicellular organisms.  The standard will

be even higher for biomarkers on Mars than for biomarkers on Earth, as the controversy

over the ALH84001 meteorite shows. McKay et al. [1996] presented four lines of evidence

for fossil remains of Martian biota in the meteorite.  Of these, the strongest evidence comes

from chains of magnetite embedded in carbonate globules.  The chains are similar to those

produced by magnetotactic bacteria on Earth, and some authors have argued that some

analogue of magnetotactic bacteria evolved on Mars.  Spurred by this claim, researchers have

subjected the meteorite and the magnetite chains to an intense scrutiny.  Recently, Gibson

et al. [2001] argued for evidence of life in two other meteorites, Nakhla and Shergotty.  While

the evidence is controversial [e.g., Thomas-Keprta et al., 2000, Golden et al., 2001, Buseck

et al., 2001], the possibility that some of the magnetite particles were synthesized on Mars

makes them an exciting subject to study.

 

To improve our chances of detecting early life on Earth and other planets, we must

develop clear and su±cient standards for biomarkers.  While many such criteria have been

suggested [e.g., Gibson et al., 2001], I will concentrate on criteria for biominerals.  Below, I

list some criteria that a biomineral should satisfy:

 

1. Difficult to synthesize inorganically.

2. Shows the fingerprint of natural selection.

3. Easy to detect in situ.

4. Well preserved.

 

While all four criteria apply to biominerals on Earth or Mars, the third is merely useful on

Earth but essential on Mars because of the prohibitive cost of bringing back samples.

At present, chains of magnetite particles have as good a chance of satisfying the above

criteria as any known biominerals.  They look especially attractive in the light of the fourth

criterion because it might be possible to detect a magnetic signature using a non-invasive

magnetic measurement.  This could be used to rapidly screen samples for further analysis.

I propose to evaluate magnetite produced by magnetotactic bacteria by the above criteria,

especially numbers 2 and 4.  The work will be theoretical because the experimental work is

further advanced than the theoretical work and is already being vigorously pursued by many

groups.

Nicholson

Department of Interior

03HQGR0021

Kinematic Mapping of 3D Fault Planes in Southern California

11/15/02-11/14/03

$40,000

In this project, I propose to focus on mapping 3D fault planes in southern California using existing, available, relocated seismicity and focal mechanism catalogs.  From the review panel, the “priority region of study is the San Bernardino and San Gorgonio Pass regions.”  The project will thus:

 

1.   Identify active subsurface faults in southern California using relocated earthquake hypocenters and focal mechanisms in space and time.  The area of focus will be the Transverse Ranges and northern Peninsular Ranges in the region around San Gorgonio Pass and San Bernardino.

2.   Develop 3D fault maps showing position, geometry, and style of active subsurface faults, and their relation to mapped surface faults and topography.

3.   Compare and analyze these results with fault patterns inferred from other models using state-of-the-art 3D visualization techniques.

4.   Present and publish results.

Niemi

National Science Foundation

EAR-0310252

Paleotopography of an Evolving Extensional Orogen, the Central Basin and Range

10/01/03-09/30/04

$126,490

This project is designed to look at the topographic evolution of a portion

of the central Basin and Range in the western United States during a period of late Cenozoic extensional

tectonism.  A variety of paleoaltimeters, geologic studies, and geophysical models have

alternately predicted that the western United States has experienced either significant late Cenozoic

uplift or substantial late Cenozoic lowering due to, or at least synchronous with, large magnitude

intracontinental tectonism.  In part these disparate results may be due to the geologic complexity

of the western United States, and the fact that many of the study areas may have undergone differing

tectonic histories in late Cenozoic time.  The central Basin and Range province, between

Las Vegas and the Sierra Nevada is an ideal locality to study the paleotopographic evolution of

the western United States because of 1) the wide spread and detailed geologic mapping that has

been completed, resulting in a fairly complete palinspastic reconstruction of Tertiary extension; 2)

recent passive and active seismic and other geophysical experiments in the region which delinieate

the crustal structure and 3) studies that have examined the evolution of the sub-Basin and Range

lithosphere through this same time period using xenoliths and the geochemistry of volcanic rocks.

A newly developed paleoaltimeter based on basalt flow vesicles is well suited for approaching

this problem due to the extensive coverage of basalts in this study area, the broad age range of

the flows, and the desert environment which keeps them relatively fresh.  We propose to sample

approximately 40 sites for paleoaltimetry across a 300 km transect from the Sierra Nevada to the

Spring Mountains, Nevada and determine the paleoelevations of these sites from late Miocene to

Pliocene or Recent time.

 

This study has broad impacts for several reasons; first it bears strongly

on the hypothesis that late Cenozoic epierogeny has affected climate, both in the United States

and globally.  The work also ties together years of work in developing map view palinspastic

reconstructions of Basin and Range extension by adding a third dimension to the deformation,

and finally, this study will be the first broad tectonic study using the newly developed altimeter.

Collaborations with both the developers of the altimeter and the analytical facilities which process

the samples should result in a stream lined process for future use of this altimeter, as well as testing

and demonstrating its use in tectonic studies.

Olsen

University of Southern California

080113

3D Ground Motion Simulation in Basins

08/01/02-03/31/04

$33,250

The project will foster the integration of 3D ground motion simulation methods and results into engineering applications.  We will validate 3D simulation methods and apply them to complex geological structures, with emphasis on urban sedimentary basins.  We propose a coordinated, multi-institutional investigation, with funding shared between the Pacific Earthquake Engineering (PEER) Center and the Southern California Earthquake Center (SCEC). The PEER and SCEC research components will be fully integrated, and the project will be structured to address the engineering and science requirements of both Centers.  A companion proposal with the same title and team of  investigators was submitted to SCEC in December 2001.

 

The project will deliver a report that (1) documents and compares the results of applying multiple

modeling techniques to past earthquakes, (2) assesses the strengths and weakness of competing

3D methodologies (in comparison with each other and with simplified methods such as 1D

simulations and standard empirical methods), (3) estimates statistical bias and uncertainty in

ground motion estimates obtained by 3D numerical modeling, (4) applies numerical simulations to

develop engineering rules to correct for basin effects in empirical estimates of ground motion.

The project will also deliver an online resource containing descriptions of the simulated earthquake

scenarios, together with the simulated ground motions.  This online documentation will serve both

the ground motion modeling and earthquake engineering research communities.

Olsen

University of California Los Alamos National Laboratory

SBB-014A

Fully Non-Linear Inversion of Dynamic Earthquake Rupture Propagation

11/01/02-10/31/03

$49,984

Numerical simulation codes (Olsen et al., 2002) are now sufficiently sophisticated to estimate ground motions in large urban areas by including large-scale, state-of-the-art three-dimensional models of sedimentary basins (Olsen et al., 1995) using high-performance computing.  However, a limiting factor in the accuracy of the predicted ground motions, even for the low frequencies, is accurate knowledge about the complexity of earthquake rupture.  Olsen et al. (1997) showed that inclusion of the heterogeneity in rupture propagation is critical for accurate prediction of the resulting ground motion around the fault which is an important part of seismic hazard assessments.  Another critical research area where accurate knowledge of rupture parameters is essential, earthquake prediction, is maybe the most important of them all.  If we can further our understanding of the conditions under which earthquakes initiate, propagate, and arrest, as well as their variations in stress and friction, we may be able to predict the occurrence of future damaging events and thereby mitigate the loss of lives and property.

 

The conventional procedure to infer information about the rupture history of large earthquakes is a linear inversion for the slip history on the fault by matching recorded and synthetic accelerograms (Wald and Heaton, 1994).  Such inversion has traditionally been carried out kinematically, which has some important limitations, in particular unphysical constraints on the rupture velocity and omitting dynamic rupture effects from the normal-stress interaction with the free surface.  For example, the latter effects can play a significant role for earthquakes on shallow faults or ruptures breaking the surface (Oglesby et al., 1998; Gottschammer and Olsen, 2001), including earlier arrival times caused by super-shear rupture velocities and an increase of peak horizontal motions by up to about a factor of three.  Therefore, when ignoring the dynamics, slip inversion may produce biased information about the rupture.

 

A more physically correct inversion would therefore take into account the dynamics of the rupture, i.e., the stress, strength, and friction parameters.  However, such inversion is highly complicated due to the strong nonlinearity of the dynamic problem, as demonstrated by Peyrat et al. (2001) who inverted for the dynamic rupture history of the 1992 M7.3 Landers, California, earthquake using a trial-and-error method.  The results by Peyrat et al. (2001) showed that the radiated waves are highly sensitive to the distribution of stress and friction parameters on the fault, an essential requirement for the inversion to work.  Here, we attempt to carry results by Peyrat et al. (2001) to a new level using a fully systematic, nonlinear inversion method.

Olsen

National Science Foundation

EAR-0003275

Forward and Inverse Modeling of Rupture Dynamics in Three Dimensions

04/01/01-03/31/04

$249,027

The proposed research is an integrated approach to significantly advance our knowledge in the field of earthquake rupture dynamics.  The work consists of three parts.

 

The first part is the development of a hybrid method for flexible and efficient modeling of dynamic rupture propagation on curved fault geometry and its radiation in a heterogeneous three-dimensional medium.  The dynamic rupture propagation is computed using the Boundary Integral Equation (BIE) Method.  The computation of radiated waves away from the fault is carried out by an efficient fourth-order staggered-grid finite-difference (FD) method.  The hybrid method enables dynamic modeling of rupture propagation on curved or multi-segmented faults in laterally and vertically heterogeneous earth models with an accurate free-surface.  In addition to the model of dynamic rupture on a single fault, the efficiency of the hybrid method can be used to model the statistics of recurrent ruptures on multiple, curved faults.  Finally, the method may be used to improve the accuracy of kinematic source implementation on extended faults.

 

The second part of the proposed research is a continuation of ongoing efforts on defining the parameters and conditions under which dynamic rupture may start, propagate, and stop.  Preliminary results indicate that there is a simple non-dimensional parameter k that controls rupture propagation.  This number generalizes previous studies in 2D and 3D by Andrews, Day, Burridge and many others.  The rupture process has a bifurcation point at a critical value k = k_c, so that for values of k less than critical, rupture does not grow, while for values slightly above critical, ruptures grow indefinitely at sub-Rayleigh or sub-shear speeds.  For values of k larger than 1.5 k_c rupture becomes super-shear in the in-plane direction.  The implications of this simple number are wide ranging and require extensive tests and analysis of modeling.  An important question here is whether propagating ruptures have ‘memory’ of the conditions under which they started, i.e., does the rupture velocity depend on the initial stress and friction on the fault?  We propose to analyze the transitions from sub-Rayleigh to super-Rayleigh speeds, and to add heterogeneity in the friction and stress on the fault.  We propose to use the 1992 Landers earthquake, which has been extensively analyzed by many studies, and kinematics is fairly well constrained, as well as the 1999 Chi-Chi, Taiwan, earthquake, to test the criticality issues for dynamic rupture.

 

The third part is to examine the feasibility of inverting for the friction or the initial stress field of a specific, large earthquake.  Preliminary studies show that the radiated waves are highly sensitive to the values of slip weakening and rate weakening friction as well as the initial stress field on the fault.  If indeed dynamic friction is feasible, the proposed research may open up the most promising approach toward understanding the dynamics of earthquakes.  It is possible that only the product of the friction and stress, i.e., the fracture energy, is resolvable.  In any case, the fracture energy parameter is invaluable to the field of rupture dynamics.  A critical question is whether even strong motion records have enough resolution for this task, and to what extent complications arise from the strong non-linear dependency of the stress and friction.  We will test several iterative inversion routines, starting with linearized least squares methods.  The initial tests will be to invert for very few degrees of freedom, and later move to finer discretizations of the inversion parameters.  We will describe the limitations and accuracy of the inversion, and attempt to apply the method to the 1992 Landers and 1999 Chi-Chi earthquakes.

 

The three parts of the proposed research all lead toward the ultimate goal of the project, namely to better our understanding of why do earthquakes start, propagate and arrest.  Such understanding may lead to successful prediction of earthquakes in the future, thereby mitigating the loss of life and property.

Oskin

University of California Mexus

SB030012

What Processes Lead to Continental Break-Up?  Opportunities for Collaboration

07/01/02-06/30/03

$15,000

Continental break-up and formation of new ocean basins are topics of exceptional academic and economic interest in the earth science community.  The states of Mexico surrounding the Gulf of California represent a world-class natural laboratory to study the formation of a young ocean basin.  The research proposed here to the U.C. MEXUS program is to begin studies of the record of continental extension in western Sonora that led to break-up of the continent and opening of the Gulf of California.  Western Sonora is an exceptional location to study these processes because it contains both an interior zone of large-magnitude intracontinental extension and a margin zone where the continent was ruptured and a new ocean basin has formed.  Investigations of the record of faulting and extension intermediate in time and space between these contrasting zones will lend new insight into the physics of continental deformation and the origin of major geologic structures of continental margins.  These studies will also have direct applicability to understanding the groundwater resources of this desert region.  The funding provided by the U.C. MEXUS program will seed a binational effort to study continental extension in western Sonora by supporting joint field studies and initial geochronologic measurements.  We anticipate that this research will lead to immediately publishable results, as well as to additional support for collaborative studies of this region.

Prothero

National Science Foundation

DUE-0231414

Collaborative Research:  Moving Data Based Inquiry Learning to the Internet

01/01/03-12/31/05

$427,432

The over-arching goal of this project is to increase science literacy of general education learners who may not become scientists.  The specific goal of this project is to create a well-researched oceanography course, live and online, widely disseminated, with a modern inquiry based pedagogy.  The design focuses on science literacy using real earth data, collaboration between learners, and a strong connection to societal issues.

 

The project is based on a successful NSF CCLI pilot project that supported the creation of software and course materials that enables online auto-graded homework assignments, scientific writing activities, on demand grade calculation, and peer interaction, with powerful instructor assessment capability.  It has been tested, refined, and evaluated in 2 live oceanography classes at UCSB.  New capability will be created to support the fully online course with collaborative projects with strong peer to peer interactions. It will be first implemented in Spring 2003.

 

An instructor team has been assembled.  The team consists of faculty representing 4 California community colleges, 2 California state colleges, 2 large state universities (not including UCSB), and a small private college.  Yearly workshops are planned to support team collaboration and dissemination of technology and pedagogy.

 

Major themes are integration of technology in education and faculty development.  We also expect to have an indirect impact on teacher education and diversity through the composition of the project team, some of whom have been active in teacher preparation and/or teach at campuses with a diverse student population.

Sorlien

Department of Interior

03HQGR0048

Digital 3D Mapping of Active Faults Beneath Santa Monica Bay, Basin Modeling

01/01/03-12/31/03

$35,000

High rate of strain translates into high earthquake hazard in the Los Angeles area.  This strain may be distributed between many low-rate faults.  If so, all active structures need attention, particularly large ones. The Santa Monica Mountains-Channel Islands (SMMCI) anticlinorium extends along the southern boundary of the western Transverse Ranges and is 220 km-long and 30-50 km-wide.  Models for this structure incorporate very large blind thrust faults.  The Channel Islands part of the structure is probably active, but whether the Santa Monica Mountains are actively folding is being debated. Immediately west of Manhattan Beach lies the 10x15 km Shelf Projection anticlinorium, which is another possibly active fault-related structure that may present hazard to Los Angeles.  Co-located active thrust faulting is manifested by M5 earthquakes (1930, 1979, 1989). Directly imaged shallow faults in our Santa Monica Bay study area tend to be dominantly transcurrent.  The E-W onshore-offshore Santa Monica-Dume fault zone separates the Santa Monica Mountains from a post-Miocene basin to the south.  We interpret this fault zone to be left-lateral on the basis of an offshore restraining segment.  The active NW-SE right-lateral Palos Verdes and San Pedro Basin fault zones seem to die out before reaching the E-W fault system.  They may, however, continue as blind faults feeding strain to shallow vertical-axis block-rotation systems decoupled by regional Miocene detachments.

 

Earthquakes rupturing major portions of the inferred Santa Monica Mountains blind would be very large and thus rare according to slip rates estimated in the Channel Island segment.  The blind thrust that we identified beneath the Shelf Projection anticlinorium could be capable of Northridge-sized events adjacent to the coastline.  Segmentation of these structures would reduce maximum size but increase rupture frequency.  The Shelf Projection anticlinorium may absorb the 3 mm/yr right slip of the Palos Verdes fault plus shortening associated with the Transverse Ranges.  Digital structure-contour maps on faults and deformed stratal horizons will provide the basis for characterizing earthquake sources directly relevant to the LA area, and can be used to model ray-focusing and ground motion from these sources.  This study integrates geology and geophysics across the land-sea interface around Santa Monica Bay.

Spera

Jet Propulsion Laboratory

1249219

UCSB Subcontract:  Rates of Magmatism:  Earth, Mars, and the Moon

02/12/03-09/28/03

$114,616

An important global-scale gauge of the 'thermodynamic state' of a terrestrial planet is the rate at which magma is generated within its interior.  A fraction of such magma buoyantly ascends and either erupts or is emplaced at shallow levels and can be studied in detail.  At a fundamental level, the history of core-mantle-crust-atmosphere-hydrosphere and biosphere interaction of a terrestrial planet is strongly dependent upon the rate at which energy is transferred from the interior to the surface.  Quantitative analyses of magmatism rates provide an important window into terrestrial planet evolution and development.

 

There are five mechanisms for the production of large volumes of magma on a silicate terrestrial planet (cryrovolcanism is not considered in this work).  These include: (1) quasi-isentropic decompression partial fusion, (2) heat-focusing by transport of fluid or melt to a restricted volume initially at subsolidus temperature, (3) volatile-induced melting, (4) viscous dissipation (e.g., tidally-driven degradation of mechanical energy to heat) and (5) impact-generated melting.  Any of these mechanisms can dominate at a particular location or time during the history of a planet.  Some examples include: MOR basaltic magmatism on Earth and possibly basaltic magmatism on Venus and Mars via mechanism  (1), generation of compositionally evolved anorogenic magmas in continental regions on Earth by injection, cooling and solidification of hotter, primitive magma in initially sub-solidus lower continental crust by mechanism (2), generation of Island Arc magmas due to volatile-triggered partial fusion in the peridotitic mantle wedge above subducting slabs via mechanism (3), melting, e.g., on Io due to mechanism (4) and finally impact melts and pressure-release magmatism associated with large bolide impact such as at Sudbury, Canada.

 

The objectives of this study are to extend and improve existing data for rates of magma emplacement and volcanic output for the Earth in different tectonic environments and to examine the factors affecting the rates with reference to the major mechanisms responsible for magma generation alluded to above. Although most focus is on modern rates, we will also examine the necessarily more sketchy Archean-Proterozoic record.  The implications of the terrestrial record for volcanism and plutonism on Mars are also considered.  The data compilation includes rates of volcanism and plutonism for individual volcanoes, plutons, volcanic and plutonic provinces; ratios of volumes of volcanic to plutonic rock for igneous activity in different tectonic settings; and the current total global rates for the Earth, as a function of tectonic environment.  The compiled data base will build and improve upon earlier work of Crisp (1984) and include better estimates of the averages and the distribution of rates, along with associated parameters of interest such as crust thickness, magma composition, and tectonic setting.  In addition to Mars, the results of this proposed research will have important implications for Venus, Io, and Mercury, and the Moon.  As an example, for lunar maria, we have extensive remote sensing data to discriminate individual flows, age dates from Apollo samples, crater density count statistics for age estimates, and flow thickness estimates at locations where craters have punched through lava flows.  Work by Rose and Spudis (2000) and Head and Wilson (1992) demonstrate the capability to derive good estimates of rates of volcanism for lunar Maria (for example, 1.6x10^-4 km³/yr for Mare Nubium).  Such rates can be compared to the rates for volcanism on Earth to help understand the fundamental geologic differences between the two planetary bodies and how extrapolations can be made to other bodies.  Similarly, the relationship between impacts and magmatism is important in planetary studies.  Intriguing patterns have emerged in the long-term periodicity of impacts and magmatism, as well as possible correlations between impacts and flood-basalt and hot-spot magmatism (e.g., Shaw, 1994; Rampino et al., 1997; Ivanov and Melosh, 2002). A better understanding of Earth’s global rate of magmatism and relationships with other processes will allow us to better understand the energy budget and thermal history of other planets.

Steidl

Brigham Young University

02-0105

Permanently Instrumented Field Sites for Study of Soil-Foundation-Structure-Interaction

10/01/02-09/30/04

$1,069,846

This proposal will provide NEES with two field laboratories for the study of SFSI, liquefaction, and lateral spreading.  The requested funds will be used to enhance existing, well-studied, and well-characterized seismic array sites:  Wildlife and Garner Valley.  The enhanced NEES sites will be capable of both active and passive experiments, including an SFSI test structure with shaker and structural instrumentation at Garner Valley.  As well as becoming part of NEES, both sites will interact with ANSS.

 

Permanently instrumented field sites for the study of soil-foundation-structure-interaction (SFSI) and soil failure address one of the identified research needs for the second round of NEES equipment/sites.  There is need to further study SFSI in real structures under seismic input, but there are always complexities with real structures that can mask understanding of the SFSI phenomena.  Study of soil failure is also complicated in urban or geologically-complex settings.  Simple, well-characterized test sites are needed to increase understanding of the physics behind SFSI and soil failure in earthquakes.

 

This proposal adds to the NEES program a unique pair of permanently instrumented sites that address this research need.  In particular, two simple sites in the seismically active Southern California region will be enhanced and brought into the NEES equipment portfolio, linked by next-generation wireless communications to the NEES grid.  The Wildlife site will provide a test facility for active and passive measurement of soil response and soil failure under dynamic loading.  The Garner Valley site will provide research opportunities for those developing tools for site characterization and for the evaluation of soil properties and how they change with time after seismic disturbance.  The project will provide unique research opportunities for studying the physics of SFSI.  The sites will also be an excellent test bed for new in-situ site characterization techniques, and new sensor technologies.  The field sites will also have an impact on undergraduate and graduate teaching programs in earthquake engineering, geotechnical engineering and engineering seismology.  Students will be able to participate in the active experiments through teleparticipation as well as on-site workshops.  Data and research from both sites will be significant to ANSS.

Sylvester

Department of Interior

02HQAG0099

Geologic Mapping of the Big Pine Mountain Faults:  A Rotated Microplate Boundary

07/01/02-06/30/03

$8,000

Interpretation of paleomagnetic data reveals that several large (100km by 50km) crustal blocks in southern California have undergone vertical-axis rotations while being translated along the San Andreas plate boundary (Figure 1).  Past studies document which crustal blocks have rotated, the amount of rotation, and when the rotation occurred (Kamerling and Luyendyk, 1985; Terres and Luyendyk, 1985; Hornafius et al.,1986, Carter et al., 1987; Schermer et al., 1996).  Proposed models offer explanations for how these rotations are accommodated and the types of structures that must exist between the rotating and non-rotating blocks (McKenzie and Jackson, 1986; Lamb, 1987; Nur et al., 1989; Luyendyk, 1991; Crouch and Suppe, 1993).  No work has been done; however, to map the block boundaries in the field and document the nature and geometry of deformation along the edges of these blocks.  The purpose of this study is to describe the boundary structures and deformation along one of these rotated block boundaries, the Big Pine fault, which is located in the western Transverse Ranges of southern California.  A detailed examination of the deformation at the boundaries of these rotated blocks is necessary to work out the kinematics of block rotation and to verify the paleomagnetic data with independent structural field evidence.

 

We selected the northern boundary of the western Transverse Ranges block for our mapping study, because the block has rotated more than 90 degrees since Miocene time (Hornafius, 1986), because abundant paleomagnetic data exist within the western Transverse Ranges block, and because a complete Cenozoic sedimentary sequence is present that can be used to make correlations across faults.  The northern boundary of the western Transverse Ranges block is also one of the few boundaries where the structures are relatively well exposed and not covered by water or recent alluvium.

Our preliminary research indicates that the Big Pine fault constitutes a significant part of the boundary between the rotated western Transverse Ranges block on the south and the unrotated Salinian block on the north.  This provisional conclusion is based on observed discontinuities across the fault such as abrupt changes in structural trends, stratigraphy, and paleomagnetic declinations.  We intend to examine the Big Pine fault and adjacent strips on each side of the fault to determine the deformational style and history along this structural boundary.  We will make a detailed geologic map, collect fault slip data and stratigraphic descriptions, make correlations, and collect additional paleomagnetic data in crucial areas where these data do not currently exist.  The mapping will focus on the south halves of the Rancho Nuevo Creek and Madulce Peak 7.5 minute quadrangles at a scale of 1:24,000.  The only presently published map of this area better than 1:100,000 scale is one at the 1:48,000 scale published in 1971 (Vedder, 1971). The mapping will be done in collaboration with USGS geologists, Scott Minor and Rick Stanley, both of whom are working along the Big Pine fault in areas to the east and west of the proposed study area.  We will consult Dr. Jack Vedder (USGS) and John C. Crowell, both retired, each of whom has mapped extensively in areas surrounding the two quads and have expressed great interest in this project, especially in the nature of the Big Pine fault itself.  The project will contribute to the US Geological Survey’s objective of geologic mapping in the western Transverse Ranges and is being coordinated with the SCAMP project chief, Dr. Doug Morton.

Tanimoto

University of California Institute of Geophysics & Planetary Physics

02-1206

Continuous Free Oscillations and its Applications to Planetary Seismology

10/01/02-09/30/03

$32,857

This is a third-year renewal request for the project ”Continuous Free Oscillations and

its Application to Planetary Seismology”.  The main objectives of this project are twofold;

(1) to understand the phenomenon of continuous oscillations of the Earth and (2)

to explore its potential applicability to planetary seismology.  This phenomenon is most

likely an example of atmosphere-solid Earth interaction, and thus proper understanding

of the continuous oscillations can only be achieved by an interdisciplinary collaboration.

Collaboration between a seismologist (Tanimoto) and a geophysicist/planetary scientist

who is very familiar with planetary boundary layers and atmospheric waves (ReVelle) is

ideal for this purpose.

 

The first goal of this proposed study is to understand this phenomenon and delineate

its cause.  During the first and the second year, we examined seasonal variations in the amplitudes

of modes and confirmed that there exist strong biannual periodicity (six months)

in all good data.  Stations in northern hemisphere as well as southern hemisphere exhibit

similar behaviors, yielding peaks in December-January-February and June-July-August.

If they were excited by atmospheric effects, they are expected to display latitudinal variations

because atmospheric activity is enhanced at mid-latitudes in both summer and

winter.  During the second year, we intend to examine this point in more detail and

clarify the spatial extent of the source of excitation.

 

The second goal of this study is to explore the potential existence of similar oscillations

in other planets.  If other planets are oscillating due to similar atmospheric effects, this

process will provide an important new approach for planetary seismology.  This is because,

by simply installing seismic instruments on the surface of planets, we may be able to

determine its normal mode frequencies.  Observed foreign frequencies will in turn provide

seismic velocity structure in the planetary interior.  This idea is attractive for a tectonically

quiet planet such as Mars because quakes are rare for such a planet and the historical

seismic approach is likely to fail.  Theoretical predictions of the modal amplitudes for

Mars will be computed in detail by the end of the second year, in preparation for the

planned mission later during this decade (the Netlander mission in 2007).

Wyss

National Science Foundation

DEB-0206762

Dissertation Research:  Phylogeny of the Rhynchosauria

08/01/02-07/31/04

$9,724

The major objective of this study is to produce a comprehensive phylogeny of all Early, Middle, and Late Triassic rhynchosaurs, including abundant new fossils of the previously fragmentary taxon from Madagascar and newly and/or incompletely described taxa from Argentina and Brazil.  A second objective is to analyze patterns of dental evolution within this ubiquitous group of Triassic herbivores. Proposed activities resulting from this research include: travel to South American, German, and South African rhynchosaur collections, detailed examination and description of dental and skeletal characteristics, construction of an all-encompassing data matrix of characters scored from first-hand observations and measurements, and parsimony and multivariate analysis to assess phylogenetic relationships within the Rhynchosauria.  Because rhynchosaurs have been used extensively to correlate Triassic terrestrial faunas worldwide, the projected impacts of this study go well beyond the benefits of an inclusive reassessment of rhynchosaur evolutionary histories.  The results of this research will help establish a worldwide biochronologic correlation of the newly discovered Middle or Late Triassic fauna from Madagascar with roughly contemporaneous faunas (particularly those found in Argentina and Brazil), and will potentially yield insights into Triassic biogeographic linkages in the Southern Hemisphere during this important time of diversification in the fossil record.

Wyss

Evolving Earth Foundation

SB030090

Unraveling the Evolutionary and Geologic History of the Central Chilean Andes Using Biochronology and Geochronology

01/17/03-09/30/03

$3,000

Paleontological discoveries in the Andes Mountains of central Chile have uncovered a remarkable archive of mammalian evolution in a region long assumed to be devoid of fossils.  These manmal remains, in turn, represent a unique chronological resource for unraveling the complex geotectonic history of this segment of the Cordillera.  This project proposes to examine the evolutionary and geologic implications of fossils recovered from Laguna del Laja, Chile, several hundred kilometers south of localities previously studied.

 

The Laguna del Laja manmal fauna recovered from southern central Chile ( 37.5 degrees S. latitude) in January 2003 illuminates several areas of Andean geology that have long been problematic.  For example, this fauna is the first of its kind to be recovered in this entire region.  Moreover, it offers a reliable (and sometimes the only) means for establishing the age of the rock unit from which it is derived, the Cura-Mallin Formation.  I propose to use paleontological information in conjunction with high-precision ⁴⁰Ar/³⁹Ar radioisotopic dating to refine age estimates for this geographically widespread formation.  A well-constrained geochronology will allow us to integrate the Cura-Mallin Formation (which constitutes more than half of the rocks exposed in this part of the range) into the larger tectonic framework for this portion of the Andes, and its fossils into the evolutionary history of South American mammals.