Becker

Texas A&M Research Foundation

F001319

The origin of organic matter and hydrocarbon in the Nankai accretionary complex, Japan

8/17/00-11/30/02

During Leg 190 a study of methane and light hydrocarbons was conducted in the sediments deposited in the Nankai Accretionary Complex offshore Japan.  In addition, bulk hydrogen (H₂) and carbon monoxide (CO) were measured in pore waters in these sediments that varied in depositional setting and temperature (3^oC to > 100^oC) from moderate to extreme.  The very low organic carbon content of the sediments and high temperatures encountered in the cores drilled during Leg 190 make the Nankai Accretionary complex a unique setting for assessing the production mechanisms for H₂ and CO (i.e. biogenic vs. abiogenic).  Thus, Nankai provided a unique opportunity to re-examine the hypothesis that microbes are capable of utilizing alternative energy sources that would support a heterotrophic subsurface ecosystem.  The pristine nature of the pore fluids (the fluids do not interact with the accretionary wedge sediments and their passage through fault zones minimizes interaction) will reduce contamination from biological sources. Preliminary data suggest that, despite the very high temperatures and pressures that exist in some extreme environments encountered in the Nankai Accretionary Complex, a low level of microbial activity is supported by the presence of organic matter in the sediment (TOC, rock-eval).  There is no evidence that microbes are using an alternative energy source to sustain themselves in this relatively organic poor environment (i.e. hydrogen from the disssociation of minerals etc.).  Thus, the notion that organisms in extreme environments are utilizing alternative energy sources (i.e. abiogenic hydrogen) needs to be re-examined. Stable carbon and hydrogen isotope studies on the sediments collected during Leg 190 are in progress to further assess the various production mechanisms (i.e. biogenic, thermogenic, catagenic) for the H₂, CO, methane and light hydrocarbons detected. 

 

Becker

National Aeronautics and Space Adiministration

NAG5-11560

Interstellar organic molecules and the rigin of life: The role of exogenous delivery

12/1/01-11/30/03

Fullerenes were also detected in sediments associated with the Cretaceous/Tertiary and Permian/Triassic boundary events.  Both of these time periods are linked to important changes in the geologic record including mass extinction, eustacy and changes in the carbon cycle.  By further exploiting the unique properties of the fullerene molecule to retain noble gases (like ³He) we are attempting to use fullerene to re-assess the link between extraterrestrial flux (bolide, cometary) and global biogeochemical changes that lead to mass extinction.  Measurements of helium, neon and argon in the PT sediments from Meishan, China and Sasayama, Japan confirm that an impact event occurred at the Permian-Triassic boundary some 250 myr ago. (Science, 291, p. 1530-1533, 2001; Becker, L., Poreda, R. J., Technical Comment - Impact Event at the 250 myr old Permian – Triassic Boundary? Science, Sept 28, 293 U3-U5 (2001).

 

Becker

National Science Foundation

OCE-0296087

Collaborative Research: Fullereness and the extraterrestrial flux of helium to the surface of the earth over geologic time.

10/1/01-1/31/04

 

The Bedout High, located offshore Canning basin in western Australia, is an unusual structure and its origin remains problematic.  K-Ar dating of volcanic samples from the Lagrange-1 exploration well indicated an age of about 253 +/- 5 Ma consistent with the Permian-Triassic boundary event.  Gorter (PESA News, pp. 33-34, 1996) speculate that the Bedout High is the uplifted core (30 km) of a circular feature, some 220 km across, formed by the impact of a large bolide (cometary or asteroidal) with the earth near the end-Permian.  Accepting a possible impact origin for the Bedout structure, with the indicated dimensions, would have had profound effects on global climate and significant changes in lithotratigraphic, biostratigraphic and chemostratigraphic indicators as seen in several Permian-Triassic boundary locations worldwide. 

 

We have re-examined some of the structural data previously presented by Gorter (1996) using additional seismic lines and have found several features that suggest an impact origin for the Bedout sturcture.  We have also coupled several impact tracers including iridium, shocked quartz, productivity collapse, helium-3, chromium-53 and fullerenes with trapped noble gases from some Permian-Triassic boundary sites in the Tethys and Circum-Pacific regions.  Our findings suggest that the Bedout structure is a good candidate for an oceanic impact at the end Permian triggering the most severe mass extinction in the history of life on the Earth. Poreda, R. J. and Becker, L. Fullerenes and Interplanetary Dust in the Permian-Triassic Boundary. in press in Astrobiology (2002).  Becker, L. Nicholson, C. and Poreda, R.J. A Re-Examination of the Bedout High, Offshore Canning Basin, Western Australia – Possible Impact Site for the Permian-Triassic Mass Extinction Event? AGU Abstract December 6^th –10^th (2002). Becker, L. Repeated Blows Scientific American pp. 64-69 March (2002).

 

Becker

National Aeronautics and Space Adiministration

NAGS-11385

Fullerenes: A new carrier-pahse for noble gases in meteorites

10/1/01-10/31/03

We have recently established fullerenes as a new extraterrestrial form of carbon in meteorites.  The noble gas ratios for He, Ne and Ar in the Murchison and Allende and Tagish Lake carbonaceous chondrites indicate that the fullerene carrier phase is most similar to the planetary component.  The very high partial pressure and temperatures needed to encapsulate noble gases in the fullerene molecule argues against their formation in the solar nebula, thus the true nature of the planetary component may be presolar. Isolation of fullerenes and trapped noble gases in the Tagish Lake carbonaceous chondrite also indicate a planetary signature. Science 293 2236-2239 (2001).

 

Boles

Department of Energy

DE-FG03-96ER14620

Fluid flow in faults: Estimating permeability and diagenetic effects in a transpressional tectonic setting, Southern California

12/1/01-3/31/03

This DOE grant supports geologic studies that document fluid movement in faults, We are using geochemical and isotopic techniques to estimate magnitude of fluid movement and nature and distribution of fault cements.  Spatial distribution of cements in the Refugio/Carneros and Wheeler Ridge faults of Southern California demonstrates the inhomogeneities of fluid movement in faults.  Studies in the Santa Barbara coastal area document the evolution of fluid movement from the basin.  Based on calcite cemented fault zones, we conclude that several hundred thousand years ago the hydrocarbon basin was overpressured and the breaking of a seal released hot formation water and hydrocarbons to the surface.  Today, the fluids are normally pressured and hydrocarbons are the principal phase escaping along faults.  The rate of escape is influenced by ocean tides and sea water movement in the fault zone.  Other studies on this grant include the work of graduate student Renee Perez, who is modeling plagioclase albitization kinetics, an important reaction for understanding formation water chemistry. Renee is also studying quartz cements related to fluid movement in reverse faults of the Maricaibo basin of Venzuela.

 

Boles/Leifer

University of California Energy Institute for Crustal Studies

SB020003

Temporal variation of a major natural gas seep, Santa Barbara Channel, California

7/1/01-6/30/03

This UCEI grant supports monitoring of natural methane seep rates from multiple locations.  The project includes the designing and construction of small monitoring tents to be deployed onto the ocean bottom.  We are testing the hypothesis that natural seeps are interconnected and that fluctuations in seep rate occur simultaneously at multiple vents over a large area.  The Shane seep complex, offshore from the UCSB campus, will be the test monitor site.  We have constructed and successfully tested a prototype tent at this location and two additional tents are being constructed to monitor gas escape rates from a total of three locations.  Preliminary background studies of the Shane seep reveal that the gas emission rate is episodic with large emissions over short time periods.

 

Burbank

National Aeronautics and Space Adiministration

NAG5-10520

Tectonic-Climate Interactions in Active Orogenic Belts: Quantification of Dynamic Topography with SRTM Data

1/1/01-2/14/03

Research funded under this project has made substantial progress in understanding the development of topography over an active orogenic belt.   The principal focus of this research has been the Kygyz Range, a 4.5 km-high mountain range in the northwestern Tien Shan orogenic belt of central Asia.  Active growth and eastward propagation of the Kyrgyz Range creates a natural laboratory to observe progressive development of a fluvially- and glacially-sculpted landscape.  We observe that glaciation plays a dominant role in the development of the drainage network over the Kyrgyz Range.  Catchments that are uplifted above the glacial equilibrium line enlarge rapidly by cirque retreat and capture adjacent non-glaciated or less-glaciated catchment area.  Fluvial response to a glacially-enlarged catchment may be initially delayed by moraine deposition within high-altitude, low-stream-power reaches, but continued enlargement enables effective transport of glacial debris and enhances fluvial bedrock incision. Fluvial incision and integration of these glacially enlarged catchments gradually imprints a steady-state relief structure on the range that combines glacial and fluvial erosional realms and processes.

 

Burbank

National Science Foundation

EAR-0196321

Strain rates, patterns, and partioning during continetal transtension

1/1/01-5/31/03

During the course of academic year 2001-2002, we completed field mapping, surveying and sample collection along the White Mountain fault system.  Field work resulted in: 1) identification of several sites along the fault system where displacement can be reconstructed using stratigraphic and geomorphic markers, 2) quantitative estimates of distributed strain across the Waucobi embayment, 3) the development of a revised stratigraphic framework for latest Pliocene lacustrine deposition in the region.  We collected ~15 samples of tephra from lacustrine and terrestrial sediments; half of these have been analyzed for geochemical correlation to eruptive centers and thus provide precise chronologic control on faulting and tectonism.  In addition, we described and analyzed soils from 5 pediment surfaces in the Waucobi embayment.  Samples for cosmogenic isotope analysis were collected from several of these pits.  Samples have been processed and we are awaiting the analytical results from Purdue’s PRIME lab.  In addition, we collected a suite of 15 samples along an elevation transect down the western front of the Inyo Mountains for thermochronometry – samples are in processing, and results should be forthcoming within the next 6 months.

 

Results from this project are being presented at two national meetings this fall:

Kirby, Burbank, Jager, Reheis, and Sarna-Wojcicki, 2002, Pleistocene Slip Rate on the Whitte Mountain Fault Zone: GSA Annual Meeting

Dawers, Sheehan, Kirby, 2002, Structural Nature of a Large Discontinuity in the Sierra Nevada Extensional Fault System: the Coyote ‘Warp’ of Northern Owens Valley, California: GSA Annual Meeting

Jager, Kirby, Burbank, 2002, Patterns of Pliocene-Pleistocene Deformation in the Waucobi Embayment, Owens Valley, California: AGU Annual Meeting

In addition, one M.S. thesis (Jager) and two manuscripts (Kirby, Burbank, Reheis, Sarna-Wojcicki – GSAB, Kirby and Dawers – Geology) are in preparation.

 

Clark

South Florida Water Management

P004163

Isotopic measurements fromt the Floridan Aquifer

8/1/00-7/31/01

An isotope study of the Floridan aquifer in south of Lake Okeechobee was initiated to study the flow pattern, groundwater ages, and water rockinteractions of seawater circulation through this carbonate aquifer.  It was hoped that glacial age seawater would be found within the aquifer system so that the glacial/Holocene change in ocean water temperature, stable isotope composition, and salinity could be determined for Straits of Florida bottom water.  These data are needed to test Lynch-Stieglitz et al. (1999) conclusion that the Gulf Stream was significantly weaker during the last glacial period.  Preliminary isotope data indicates that glacial seawater is not stored within the Floridan aquifer suggesting that the circulation time is less than 10,000 years.  The seawater water chemically evolves during its transit, losing Mg and gaining Ca.  Rates of these chemical changes are currently being evaluated.  Funding for this project was obtained from the South Florida Water Management District and through a collaborative research project with Los Alamos Nation Laboratory CULAR program.

 

Clark

CULAR/UC Los Alamos National Laboratory

10010

CULAR-Insight into gulf stream changes during the last glacial period using paleotemperatures in the Floridian Aquifer

10/1/01-9/30/02

An isotope study of the Floridan aquifer in south of Lake Okeechobee was initiated to study the flow pattern, groundwater ages, and water rock interactions of seawater circulation through this carbonate aquifer.  It was hoped that glacial age seawater would be found within the aquifer system so that the glacial/Holocene change in ocean water temperature,  stable isotope composition, and salinity could be determined for Straits of Florida bottom water.  These data are needed to test Lynch-Stieglitz et al.  (1999) conclusion that the Gulf Stream was significantly weaker during the last glacial period.  Preliminary isotope data indicates that glacial seawater is not stored within the Floridan aquifer suggesting that the circulation time is less than 10,000 years.  The seawater water chemically evolves during its transit, losing Mg and gaining Ca.  Rates of these chemical changes are currently being evaluated.  Funding for this project was obtained from the South Florida Water Management District and through a collaborative research project with Los Alamos Nation Laboratory CULAR program.

 

Clark

UC Institute of Geophysics & Planetary Physics

02-GS-018

Imaging time scales of flow and transport within the mission tunnel fracture rock system during El Niño conditions

10/1/01-9/30/02

Chemical weathering rates provide key insights into global cycling of carbon dioxide and nutrients on many temporal and spatial scales. In this study, the temporal variability of the relative contributions from the soil and groundwater zone to the overall weathering flux are examined. We proposed to use our newly developed field technique (Radamacher et al., 2001) for determining chemical weathering rates in the groundwater zone in the Loch Vale catchment, Colorado.  Substantial data on stream chemistry, stream flow, soil weathering, and spring chemistry already exists for this catchment. Combining the results of our study with the existing data will enable us to determine the groundwater contribution to the catchment hydrochemistry, a fundamental question in catchment hydrochemistry.

 

Clark

Water Replenishment District of Southern California

SB020079

8/1/01-7/31/03

 

Clark

Orange County Water District

211634

8/1/00-2/28/03

 

Gans

University California Mexus (UC MEXUS)

SB020034

Structural and volcanic evolution of southern Sonora

7/1/01-12/31/02

P. Gans and students (M. Wong, K. Blair, and I. MacMillan) and collaborator Jaime Roldan Quintana (UNAM-Hermosillo) spent much of winter quarter (2002) conducting field work and sampling of a transect across southern Sonoran. The goal was to make a preliminary assessment of the magnitude and timing of extension across this portion of the Mexican Basin and Range province by examining a few key areas in detail. This preliminary geologic investigation and subsequent 40Ar/39Ar analyses has led us to a number of new conclusions regarding the evolution of this rifted margin: (1) The inception and timing of major extension appears to have migrated westward across the province, from the Oligo-Miocene (25-20 Ma) in the east, to Early Miocene (20-16 Ma) in central Sonora, to Middle Miocene  (12-10 Ma) along the western coast. (2) Most of the extension in Sonora predates the cessation of sunduction at this latitude and is not directly linked to the transtensional opening of the Gulf of California (3) The metamorphic core complexes of Sonora were unroofed mainly in the early to Middle Miocene and are synchrynous with the core complexes in the U.S. (4) Magmatic activity also migrated westawrd across Sonora and is often closely associated with local extension.

 

Hacker HBN03

National Science Foundation

EAR-9809840

Collaborative Research: The thermal, petrological and seismological structure of subducting oceanic lithosphere

7/15/98-3/31/02

New thermal-petrologic models of subduction zones are used to test the hypothesis that intermediate-depth intraslab earthquakes are linked to metamorphic dehydration reactions in the subducting oceanic crust and mantle. We show that there is a correlation between the patterns of intermediate-depth seismicity and the locations of predicted hydrous minerals: earthquakes occur in subducting slabs  where dehydration is expected, and they are absent from parts of slabs predicted to be anhydrous. We propose that a subducting oceanic  plate can consist of four petrologically and seismically distinct layers: 1) hydrated, fine-grained basaltic upper crust dehydrating under equilibrium conditions and producing earthquakes facilitated by dehydration embrittlement; 2) coarse-grained, locally hydrated gabbroic lower crust that produces some earthquakes during dehydration but transforms chiefly aseismically to eclogite at depths beyond equilibrium; 3) locally hydrated uppermost mantle dehydrating under equilibrium conditions and producing earthquakes; and 4) anhydrous mantle lithosphere transforming sluggishly and aseismically to denser minerals. Fluid generated through dehydration reactions can move via at least three distinct flow paths: percolation through local, transient, reaction-generated high-permeability zones, flow through mode-I cracks produced by the local stress state, and post-seismic flow through fault zones.

 

Hacker HBN04

National Science Foundation

EAR-9814889

Exhumation of ultrahigh-pressure rocks in the Scandinavian Caledonides

1/15/99-12/31/02

The Solund-Hyllestad--Lavik area affords an excellent opportunity to understand the ultrahigh-pressure Scandian orogeny because it contains a near-complete record of ophiolite emplacement, high-pressure metamorphism, and large-scale extension. In this area, the Upper Allochthon was intruded by the 434 Ma Sogneskollen granodiorite and thrust eastward over the Middle/Lower Allochthon, probably in the Wenlockian. The Middle/Lower Allochthon was subducted to ~50 km depth and the structurally lower Western Gneiss Complex was subducted to eclogite-facies conditions at ~80 km depth by ca. 410-400 Ma. Within <5-10 Myr, all these units were exhumed by the Nordfjord-Sogn detachment zone, producing shear strains >100.  Exhumation to upper crustal levels was complete by 403 Ma. The Solund fault produced the last few km of tectonic exhumation, bringing the near-ultrahigh-pressure rocks to within ~3 km vertical distance from the low-grade Solund Conglomerate.

 

Hacker HBN05

Woods Hole Oceanographic Inst.

A100169

Constraints on the genesis of continental crust via arc magmatism: Geology, geochemistry, structure and physical propeties of the Talkeetna arc crustal section, south central Alaska

8/1/00-7/31/02

The accreted Talkeetna arc, exposed in the Chugach Mountains of south-central Alaska, represents a cross section from the Moho to surficial volcanic deposits of a Jurassic intra-oceanic arc. We are using SIMS and partial dissolution-TIMS U/Pb zircon analyses of plutonic rocks in the Talkeetna arc to study how island arcs grow, evolve, and morph into continental crust.Our partial dissolution analyses (PDA), following the chemical abrasion technique developed by Mattinson (2000, 2001a, 2001b), used high-T (800 =B0C) annealing of radiation damage, followed by successive acid digestions of grain populations, to generate reproducible high precision ages. Low-T (160-170 =B0C) "clean-up" digestions typically showed signs of Pb loss, consistent with removal of discordant zircon, whereas high-T (>170 =B0C) and residue steps gave concordant age plateaus. Repeat analyses of samples showed similar dissolution patterns and ages agreed within two sigma errors. The SIMS and TIMS U/Pb zircon analyses from the Talkeetna arc yielded ages of 184.3 =B1 0.4 Ma, 185.0 =B1 0.4 Ma, 186.6 =B1 0.4 Ma, 192.4 =B1 2.9 Ma, 193.2 =B1 0.4 Ma, and 198.6 =B1 0.4 Ma, indicating that the arc was active from ~184-199 Ma. Previous 40Ar/39Ar hornblende cooling ages for the arc range from ~175-182 Ma, suggesting a total arc lifespan of ~20 My. This is consonant with fossil ages within arc volcanic rocks that range from early Sinemurian to upper Toarcian

(~180-202 ) and biochronology that bounds arc growth between Late Triassic and early Bajocian (~169-206 Ma). Intermediate to felsic plutonic rocks in the Talkeetna Mountains intrude the volcanic carapace of the arc, but were not previously considered to be part of the Talkeetna arc. Our new SIMS and TIMS ages of 163.9 =B1 3.6 Ma, 170.0 =B1 4.2 Ma, 171.3 =B1 5.1 Ma, 175.6 =B1 0.4 Ma, 180.8 =B1 2.7 Ma, and 183.8 =B1 2.1 Ma, overlap the ages reported above for the Chugach Mountains, suggesting that portions of the intermediate plutonism could be related to the Talkeetna arc. Our new age data from the Talkeetna and Chugach Mountains may explain the apparent paradox of intermediate continental crust being produced by the accretion of mafic intra-oceanic arcs. The lifespan of the Talkeetna arc, combined with Raleigh-Taylor instability modeling by Jull and Kelemen (2001) and thermobarometry on lower crustal garnet gabbronorites (Mehl et al., 2001), suggests that the lower crust of the Talkeetna arc could have become convectively unstable, and sunk into the asthenosphere prior to accretion. The removal of mafic lower crust would drive the bulk arc composition toward more continental values. Additionally, previously unrecognized intermediate arc plutonic rocks in the Talkeetna Mountains would lead to a more intermediate composition for the Talkeetna arc and also help solvethe arc paradox.

 

Hacker HBN06

National Science Foundation

EAR-0003568

Collaborative Research: Unites States-China scientific cooperative project: subduction and exhumation of ultrahigh-pressure rocks-field and drilling studies in Eastern China

8/1/01-7/31/03

High-pressure metamorphism and ophiolite emplacement (Songshugou ophiolite) attended suturing of the Yangtze craton to Rodinia during the ~1.0 Ga Grenvillian orogeny. The Qinling microcontinent then rifted from the Yangtze craton at ~750 Ma. The Erlangping intraoceanic arc formed in the Early Ordovician, was emplaced onto the Qinling microcontinent in the Ordovician-Silurian, and then both units were accreted to the Sino-Korea craton before being stitched together by the ~400 Ma Andean-style Qinling arc. Subsequent subduction beneath the Qinling-Sino-Korean plate created a Devonian-Triassic accretionary wedge that includes eclogites, and formed a coeval volcanoplutonic arc that stretches from the Longmen Shan to Korea. In the Late Permian-Early Triassic, the northern edge of the South China Block was subducted to >150 km depth, creating the diamond- and coesite-bearing eclogites of the Dabie and Sulu areas. Exhumation from the mantle by lithosphere-scale extension occurred between 245 and 195 Ma during clockwise rotation of the craton. The Yangtze-Sino-Korea suture locally lies tens of km north of the exhumed UHP-HP part of the South China Block, implying perhaps that the very tip of the South China Block was not subducted, or that the UHP-HP rocks rose as a wedge that peeled the upper crust of the unsubducted South China Block from the lower crust. The Tan-Lu fault is an Early Cretaceous to Cenozoic feature. The apparent offset of the Dabie and Sulu UHP terranes by the Tan-Lu fault is a result of this Cretaceous to Cenozoic faulting combined with post-collisional extension north of Dabie.

 

Kirby

University of Kansas

FY2002-041

Kansas Subcontract

9/26/01-9/25/02

During the course of academic year 2001-2002, Kirby completed ~21 days of field mapping and surveying along the Panamint Valley fault system.  The primary conclusions of this work are: 1) the normal fault system along the western flank of the Panamint Mountains is active at a low angle, 2) active slip is transferred from Searles Valley, across the Slate Range, and contributes additional slip to the Panamint Valley fault, 3) morphologic features suggest that a significant surface rupture occurred on the Ash Hill fault in recent time.  We are currently working to develop a soil chronosequence for  Pleistocene deposits in the region – we have selected sites, and plan to conduct sampling early in 2003.

 

Preliminary results from this project are being presented at the GSA Annual Meeting this fall:

Walker, Andrew, Kirby, 2002, Structural Configuration of Transtension in a Portion of the Southwestern Basin and Range: GSA Annual Meeting

In addition, one manuscript is in preparation (Kirby et al. – Active slip on a low-angle normal fault system).

 

Kneller

Consortium: BHP Billiton Petroleum, British Petroleum-Amoco, Conoco, Statoil

SB020105,SB200088, SB020122,SB20103

Three Dimensionional Heterogeneity Of Submarine Channel-Levée Systems

6/1/01-7/31/04

This project, funded by BHP-Billiton, BP and Phillips-Conoco, utilizes a combination of outcrop and 3D multichannel seismic data to constrain the lithofacies architecture of submarine channel systems. The results, in combination with work on the Nile Delta by the PI (Samuel et al, in press; Kneller, in review) serve as a basis for process-based models for submarine channel evolution. Currently the project employs one graduate student researcher and a part-time research assistant, and partially supports the PI's salary. Several months of field-work have been undertaken in Baja California, exploiting the natural three-dimensionality of the outcrop, using both conventional and digital, GIS-based mapping techniques using geo-referenced DEMs generated with reflectorless laser range-finding techniques.

 

Kneller

Consortium: BHP Billiton Petroleum, Statoil

SB020104, SB020103

The Impact Of Mass Transport Complexes On Turbidite Hydrocarbon Reservoirs

6/1/01-7/31/04

This project is supported by BHP-Billiton and the Norwegian state oil company Statoil. It is based on outcrop studies (Kneller et al, in press) and 3D multichannel seismic data, and partially supports the PI; a post-doctoral researcher is currently sought for this project. Preliminary outcrop work has been undertaken in Argentina, France Spain and southern California. Acquisition of an existing industrial 3D seismic survey from the deep offshore of Brunei is under way.

 

Kneller

BHP-Billiton Petroleum

SB020106

Plio-Pleistocene of the Atwater foldbelt (3D seismic study)

1/1/02-12/31/02

Funded by BHP-Billiton this project is based solely on interpretation of 3D multichannel seismic data. It involves description of the Plio-Pleistocene depositional systems of the deep offshore of the Esatern Gulf of Mexico including description of the geometry and scale of architectural elements and their stratigraphic stacking patterns, and also description of the post-depositional modification by gravity driven processes, like sliding, spreading and creep. Most of the effort to date has been devoted to setting up the 3D seismic interpretation software on a dual-screen Sun workstation, plus data loading and management.

 

Kneller

University of Leeds

SB20081

Collaboration with University of Leeds, UK

6/1/01-7/31/04

Ongoing involvement with the Leeds University (UK) Turbidites Research Group, initiated by the PI in 1992, has involved collaboration on experimental investigation of turbidity currents, and development of physical models for the interpretation of turbidite depositional facies based upon physical and numerical experiments (Kneller & McCaffrey, in press).

 

Lavallee

National Science Foundation

EAR-9972987

Modelling of Hysteretic and Anelastic Soils: from laboratory data to earthquake strong ground motion

7/15/99-6/30/02

The main objective of this research project is to study nonlinear effects in earthquake strong ground motion.  The premise is that nonlinear soil dynamics are essential to a full understanding of earthquake shaking.  For this purpose we have developed a robust and simple model of nonlinear soil dynamics to study seismic wave propagation.  The model includes nonlinear effects such as anelasticity, hysteretic behavior (also known as the memory effect), and lost of stiffness due to pore water pressure.

 

To understand the behavior of the soil during strong shaking we have developed a general formulation of hysteresis based on the Masing rules.  The generalized Masing rules provide a framework for understanding the nonuniform dilation and translation of stress-strain loops for a material subject to non-periodic stresses (or strains). This new hysteresis formulation has several interesting features.  It has a functional representation and it includes the Cundall-Pyke hypothesis and Masing original formulation as special cases.  In its most elementary implementation, the generalized Masing rule is even simpler than the Masing and extended Masing rules.  The model depends only on one free parameter named the fiducial point.  This parameter controls the size of the loop in the stress-strain space and therefore can be related to the amount of energy dissipated through the nonlinear property of the material.  We have derived a relationship between the anelastic damping of a stress-strain loop and the fiducial point for cyclic loadings. Finally we have developed a code to compute seismic wave propagation throughout nonlinear geomaterial. In this code, the numerical integration of the nonlinear model is performed using a velocity-displacement-stress staggered grid second order finite difference formulation.  The boundary conditions correspond to traction free conditions at surface.  Rigid and elastic boundary conditions can be specified at the soil-rock interface.  The nonlinear code is called NOAH.

Lavallee

University of Southern California

572726

Modeling of nonlinear strong ground motion during the 1994 Northridge earthquake at the Van Norman Dam Complex

2/1/99-1/31/02

 

SCEC sponsored studies and strong motion data recorded during the 17 January 1994 Northridge earthquake (M_w 6.7) have been used to determine the presence of nonlinear effects in strong ground motion.  The data available included borehole velocity profiles, weak to strong motion records, and dynamic soil laboratory tests. The nonlinear model formulation includes effects such as anelasticity, hysteretic behavior —also known as the memory effect— and cyclic degradation due to pore water pressure.  In this study, two situations have been investigated; one that includes the effect of pore pressure (effective stress analysis) and the second without it (total stress analysis).

 

Strong motion data recorded during the 17 January 1994 Northridge earthquake have been used to validate the nonlinear soil model. Signals recorded at several sites are good candidates to investigate nonlinear effects.  Four sites have been selected for this project: the Jensen Generator Building (JMB or JFP), the Newhall Fire Station (NWH) site, the Rinaldi (RIN) site and the Knoll Elementary School (KES or SMI).  For each site, measurement of ground motion observed at the near-by bedrock site has been coupled with the nonlinear model to generate scenarios of ground shaking.

 

The results of the numerical experiments conducted with these sites support the assumption that pore pressure cyclic mobility did contribute significantly to the ground shaking observed at the surface for the JMB and the SMI sites. Depletion of the high frequency in the signal is in good agreement with both the recorded and synthetic accelerations of the JMB and the SMI sites. Although nonlinear effects took place at NWH site, it is not clear that pore pressure plays a significant part in the recorded motion.

 

Lavallee

United States Geological Survey

01HQGR0049

Modeling and estimates of nonlinear effects in strong earthquake motion for the los Angeles areas

2/1/01-9/30/02

In this project, we have pursued the development and validation of a robust and simple model of nonlinear soil dynamics to study seismic wave propagation. The nonlinear model formulation includes effects such as anelasticity, hysteretic behavior —also known as the memory effect— and cyclic degradation due to pore water pressure.  One objective of this project is to validate the model with seismic observations.  For this purpose the model is used to propagate real earthquake time histories.  The synthetic acceleration time histories are compared to the recorded acceleration time histories.

 

Strong motion data recorded during the 17 January 1994 Northridge earthquake have been used to validate the nonlinear soil model. Signals recorded at several sites are good candidates to investigate nonlinear effects.  Four sites have been selected for this project: the Jensen Generator Building (JMB or JFP), the Newhall Fire Station (NWH) site, the Rinaldi (RIN) site and the Knoll Elementary School (KES or SMI).  For each site, measurement of ground motion observed at the near-by bedrock site has been coupled with the nonlinear model to generate scenarios of ground shaking. The results of the numerical experiments conducted at these sites support the assumption that a nonlinear effect contributes significantly to the ground shaking observed at the surface of three (JMB, NWH and SMI) of the four sites under study.

 

Nicholson, Kamerling

Department of Interior/United States Geological Survey

02HQGR0011

Re-evaluation of fault slip, Geodetic Strain, and Seismic Hazard

in the Light of Active Subsidence, Compaction, and 3D Fault Geometry

11/1/01-10/31/02

Geologic and geodetic data indicate that the Ventura basin currently accommodates high rates of oblique crustal strain, including components of regional tectonic rotation. Convergence and rapid subsidence across the Ventura basin has produced uplift rates that exceed 10 mm/yr and one of the thickest sections of Plio-Pleistocene strata ever found.  Significant amounts of oblique convergence (up to 7 mm/yr) have also been documented across the eastern Santa Barbara Channel and western Transverse Ranges.   This deformation represents a significant seismic hazard, and is presumed to be accommodated by  active faulting, folding, and tectonic uplift. 

Our results suggest that active faults that bound deep subsiding basins often exhibit significant non-planar 3D fault geometry.  Some of this non-planar geometry is the result of non-tectonic, non-elastic finite strain related to subsidence and compaction of basin sediments and gravity-sliding towards the basin of uplifted footwall rocks. A prime example occurs along the San Cayetano fault that bounds the eastern Ventura basin. Detailed structure contour maps and cross sections of the fault surface derived from industry subsurface well data reveal a fault geometry reminiscent of thrust nappes in the western Alps.  At shallow levels, a thin-skinned thrust sheet (the Modelo Lobe) with low dip extends out in front of the deep, steeply-dipping fault segment by over 4 km, is nearly 2 km thick, and occupies over 60 cubic km.  This geometry is strongly indicative of gravity-driven failure resulting from crustal shortening, hanging-wall uplift, and basinward tilt enhanced by footwall subsidence and compaction.  Failure of this mega-slide off the hanging-wall block most likely occurred within the Rincon Formation, a ~400-m thick ductile shale sequence that often accommodates bedding-plane or detachment slip.  Further reactivation of the slide may have been accommodated by additional shale layers within the Modelo Formation, and augmented by the presence of overpressured fluids trapped below the base of the slide as a result of continued sediment compaction and overburden loading.

 

The thrust-nappe geometry of the San Cayetano fault has significant implications for how the fault might behave during dynamic rupture.  Dynamic slip may be inhibited at shallow levels by the presence of the slide and the change in fault dip with depth; however, if the shallow thrust sheet does fail, the shallow slip may or may not be related to tectonic slip on the deep fault segment.  If the thrust-nappe geometry is the result of an ancient gravity slide, the slide can be reactivated independent of slip at depth and/or aseismically.  Large ruptures may reactivate the slide, either by dynamic triggering of the weak slide surface or by statically pushing the thrust wedge from behind.  In either case, observations of near-surface slip or large slip events at the toe of the slide may not be indicative of tectonic slip or large earthquakes at depth on the fault. The hazard associated with such deep-seated slides is increased by their possible occurrence in oversteepened terrain, their large potential slip (unrelated to accumulated elastic strain), and by the high accelerations that may be produced if dynamic rupture is abruptly terminated at shallow depth when it encounters the slide

 

Olsen

Institute of Geophysics and Planetary Physics

01-1028

Fault rupture, nonlinear grund motion and whole basin attenuation moddeling: addvances toward accurate preddiction of gground motion during a major earhtquake or explosion

10/1/00-6/30/02

University of California

SBB-014A

Fully non-linear invversion of dynamic earthquake rupture propogation

10/1/00-9/30/01

Institute of Geophysics and Planetary Physics

02-1028

Fault rupture, non-linear ground motion and whole basin attenuation

10/1/01-9/30/02

In collaboration with Dr. Chris Bradley, Los Alamos Natl. Laboratories and Prof. Steve Day, San Diego State University, I used our joint implementation of the coarse-grained visco-elasticity approach in the 3D staggered-grid finite-difference code developed by Olsen (1994) to estimate the distribution of anelastic attenuation which provides the best fit between synthetic and recorded peak velocities for the 1994 Northridge earthquake. We find that the near-surface material with S-wave velocity (Vs) as low as 500 m/s significantly affects the long-period peak ground velocities,compared with simulations in which the S-wave velocity is constrained to 1 km/s and greater. Anelastic attenuation also has a strong effect on ground motion amplitudes, reducing the predicted peak velocity by a factor of up to 2.5, relative to lossless simulations.The results suggest that for the near-surface sediments (Vs< 1.5 km/s), Qs=0.02 Vs (m/s) and Qp=0.1 Qs provide the best results. This is somewhat surprising, as previous assumptions seem to rely on much less lossy parameters in the shallow material.

 

Olsen

Jet Propulsion Laboratory

1232380

Which rupture dynamics parameters can be estimated from strong ground motion data?

8/3/01-4/30/02

We examined to what extent geodetic (inSAR and GPS) data, in addition to strong motion data, can help constrain the dynamic rupture propagation of the 1992 M7.3 Landers, California, earthquake where high-quality strong motion and geodetic data are available, and previous modeling studies have constrained the rupture propagation. We computed the three-dimensional area-wide distribution of final displacement on the ground surface for the three dynamic rupture models, as well as a model with constant slip and a three-segment fault model with heterogeneous slip. While the overall shape of the fringes are well reproduced by all models, a direct comparison with the data is only possible for the synthetics from the three-segment model. Thus, inSAR data provide a strong constraint on the geometry of the fault. The shape and amplitude of the fringes for the synthetic interferograms from a constant slip distribution are much smoother and smaller, respectively, compared to those generated by the more realistic heterogeneous models. Therefore, the modeling of SAR interferograms provides a constraint on the spatial variation of the slip distribution. We find the same conclusions from the GPS modeling. However, due to the larger spatial coverage of inSAR compared to that of GPS data, only slight improvement is obtained by including GPS data in the kinematic slip inversion. The main benefit of the GPS data is obtained 5-10 km off the fault where the co-seismic interferogram has poor resolution.

 

Olsen

National Science Foundation

EAR-0003275

Forward and inverse modeling of rupture dynamics in 3D

4/1/01-3/31/04

We have generated three dynamic models of the Landers earthquake using inversion of strong motion data. These rupture models use a single, vertical, planar fault segment with heterogeneity of either the initial stress, the yield stress, or the slip-weakening friction. Although the dynamic parameters for these models are inherently different, all the simulations are in agreement with strong motion, GPS, inSAR, and field data for the event. The three models are end-members of a large family of dynamically correct models, and the rupture for the Landers earthquake is likely a combination of these models, as intuitively, all the parameters must be heterogeneous. The rupture propagation and slip distributions obtained for each model are similar, thus we have showed that the solution of the dynamic problem is non-unique. In other words, it may not be possible to separate strength drop and Dc using rupture modeling. Instead, we propose to characterize dynamic rupture propagation by the local non-dimensional parameter kappa introduced by Madariaga and Olsen (2000), which is expressed in terms of the initial and yield stress as well as Dc, by balancing the fracture energy necessary for the creation of new crack surface, versus the energy provided by the elastic stress drop while the crack advances. The most important implication of kappa is that earthquakes seem to rupture under conditions that are extremely close to critical conditions.

 

Olsen

National Science Foundation

EAR-0113377

ITR/IM/AP: Webism 3D: A web-based system for generation, storage and dissemination of earthquake ground motion simulations

4/1/01-3/31/04

Synthetic time histories from large-scale 3D ground motion simulations generally constitutelarge 'data' sets which typically require 100's of Mbytes or Gbytes of storage capacity. For the same reason, access to a researchers simulation output, for example for an earthquake engineer to perform site analysis, or a seismologist to perform seismic hazard analysis, is typically a tedious and long procedure. To alleviate this problem, Aaron Martin and I are developing a web-based ``community model'' (websim3D) for the generation, storage, and dissemination of ground motion simulation results. Websim3D will initially be based on the nine long-period finite-difference (FD) earthquake scenario simulations carried out for the Los Angeles basin by Olsen (2000). Websim3D will allow user-friendly and fast access to view and download such simulation results for a specific region. This information includes images of ground motion response (area-wide peak displacements, peak velocities, peak accelerations, and durations), animations of wave propagation, and time histories for simulated ground motions for hypothetical and geological reasonable earthquake scenarios for the Los Angeles region. In addition, it will be possibl to view or download the parameters for the earth model used in the 3D simulations of wave propagation. The user-friendly access to the simulated ground motion time histories will allow seismologists and engineers to analyze the broadband synthetic ground motions for desired earthquake scenarios at sites of interest.

 

Olsen

DOI/USGS

01HQGR0040

Simulation of three-dimensional ground motion in Los Angeles from earthquakes in southern California

1/1/01-9/30/02

I did a thorough search for distributions of anelastic attenuation parameters for P (Qp) and S (Qs) waves in the Los Angeles Basin by fitting 0-0.5 Hz peak velocities for data and synthetics for the 1994 Northridge earthquake. The search include piece-wise linear ratios of the local S- (Vs) and P- (Vp) wave velocities. Our preferred Q model is Qs/Vs= 0.02 (Vs in m/s) for Vs less  than 1-2 km/s, and much larger Qs/Vs (0.1, Vs in m/s) for layers with higher velocities. The simple model reduces the standard deviation of the residuals between synthetic and observed natural log of peak velocity from 1.14 to 0.27, relative to simulations for the lossless case. The anelastic losses have their largest effect on short-period surface waves propagating in the Los Angeles basin, which are principally sensitive to Qs in the low-velocity, near-surface sediments of the basin. The low-frequency ground motion simulated here is relatively insensitive to Qp, as well as to the values of Qs at depths greater than roughly that of the 2 km/s S-wave velocity isosurface. The attenuation model is used to simulate area-wide ground motion for 7 earthquake scenarios, including approximations of the 1994 M6.7 Northridge, the 1987 M5.9  Whittier, and the 1933 M6.4 Long Beach events, as well as M6.75 earthquakes on  the Whittier-Narrows, Santa Monica, Palos Verdes, and Elysian Park faults.

 

Olsen

University of Southern California

075369

Direct measurment of the slip-weakening distance from near-fault strong motion data

02/01/01-01/31/02

A relation between the breakdown time of shear stress, Tb, and the time of peak slip-velocity, Tpv, was recently established using numerical simulations in a slip-weakening model (Mikumo et al., 2002). In particular, the study suggested that the slip displacement at time Tpv on the fault provides a reasonably accurate value of Dc for dynamic rupture simulations.

 

Here, we take this idea a step further and attempt to estimate an apparent value of the slip-weakening distance (Dc') from near-fault strike-parallel strong motion records. The main idea is that, close to the fault trace, the strike-parallel component of the particle velocity is an approximation of the slip velocity on the fault. Our results suggest that Dc in a slip-weakening model can be estimated within an error of about 50% as the ground displacement at the time of the peak slip-velocity Tpv from the near-field fault-parallel component of ground motion.  This technique may provide the only estimate of Dc independently of the fracture energy.

 

Olsen

University of Southern California

075369

3D Ground motion simulation in basins

02/01/01-01/31/02

The ground motion simulation code verification study in southern California (co-sponsored by PEER) continues, where five different  groups have compared synthetics for simulations in numerical models of increasing complexity. The comparisons for simple halfspace and layered models show excellent agreements between the synthetics for point sources or propagating ruptures on vertical or dipping faults  from the different groups. Current efforts concentrate on validations for the 1994 Northridge earthquake in the SCEC 3D-velocity model version 2, including both elastic and anelastic models as well as comparison of synthetics to data.

 

Olsen

University of Southern California

075369

Fully three-demensional, multi-scale waveform tomography for the Los Angeles basin and the surrounding area

02/01/01-01/31/02

In collaboration with Prof. Tom Jordan and Dr. Li Zhou of USC I am preparing to conduct a 3D tomography study for the seismic velocities in the LA Basin and its immediate neighboring regions. We will use waveform-based measurements such that more information in seismic records can be utilized to provide better constraints to the velocity structure. We are using an accurate fourth-order finite-difference method without approximations to compute sensitivity or Freschet kernels of the measurements. The inversions are pursued in a multi-scale fashion, starting from lower frequency and inverting for larger-scale structures and gradually progressing to higher frequencies and smaller-scale structures.

 

Olsen

University of Southern California

075369

How can we improve ground motion estimates by lessons learned from rupture dynamics?

02/01/01-01/31/02

The dynamic modeling study by Oglesby et al. (1998) showed significant asymmetric near-source ground motion caused by dipping faults. They found larger ground motion on the hanging wall caused by time-dependent normal-stress interaction between the fault and the free surface,and that trapping of seismic energy between the fault and free surface significantly affects the ground motion. Here we use a fourth-order finite-difference  method and the mixed boundary condition with a rate- and slip-weakening friction law used by Nielsen and Olsen (2000) for the 1994 M6.7 Northridge earthquake. Preliminary results for a 45-degree dipping thrust fault (Gottschaemmer and Olsen, 2001) suggest that inclusion of these effects increases the peak displacements and velocities above the fault by factors up 3.4 and 2.9 including the increase in moment due to normal-stress effects at the free surface. The results suggest that dynamic interaction with the free surface can significantly affect the ground motion for faults buried less than 1-3 km.

 

Archuleta/Olsen

University of Southern California

069203

ITR/AP: The SCEC Community Moddeling Environment: An information infracstructure for sysemt-level earthquake research: UCSB

10/01/01-09/30/03

The two main efforts within the SCEC ITR Project are referred to as Pathways 1 and 2. Pathway 1 aims at generating several different seismic hazard analysis estimates, and Pathway 2 will provide physics-based wave propagation simulations including visualization, new standards for I/O and links between modules. Pathway 2 can be used independently, or as a means to improve seismic hazard analysis in pathway 1. Both Pathways will be designed through user-friendly web-based interfaces. Olsen acted as the coordinator for Pathway 2 efforts within the SCEC ITR Project, through a series of meetings in southern California in 2002. Several working groups were formed to address specific goals, such as development of a browser-based capability to extract information from 3D velocity models, define standard formats for the source definition and model input and output, using the GRID to submit simulations on remote platforms, and common formats for synthetics and recorded accelerograms.

 

Kamerling/Sorlien

DOI/USGS

02HQGR0013

Structure and kniematics along the thrust front of the trasvers ranges: 3D digital mapping of active faults in Santa Monica Bay using  refelction, well, EQ data

11/1/01-10/31/02

USGS: This project is to map active faults and folds in northeast Santa Monica Bay, continuing SCEC-funded work in northwest Santa Monica Bay. The maps are both digital structure contour maps of faults surfaces, and trace maps of faults at the seafloor. The area includes E-W faults and NW-SE faults. The main surface E-W fault is the Santa Monica fault. We mapped an offshore fault, the Dume fault, to align with the Santa Monica fault across a relatively short gap in our data coverage. The relationship of folding to bends in the trace of the fault is consistent with left-lateral slip. Two NW-SE faults project to intersect the Santa Monica-Dume fault. The eastern of these, the Palos Verdes fault, dies out in the shallow sediments and does not reach the Dume fault (as suggested by Fisher et al. of USGS). The western of these, the San Pedro Basin fault, does intersect the Santa Monica-Dume fault. It is associated with very young seafloor folds-that may postdate ~100 ka. We mapped a buried low-angle fault across Santa Monica Bay that is associated with a large fold that forms the “Shelf Projection west of Manhattan Beach. USGS multibeam bathymetry is being viewed in the 3D visualization software GOCAD together with the structure maps and slip planes of earthquakes. Lowstand shorelines around the shelf projection have been identified, and are precise strain markers. Graduate student Kris Broderick has been trained in seismic reflection interpretation, digital map construction, use of GOCAD and other softwares, and use of logs from petroleum test wells. We also spent substantial time precisely siting tracklines for a USGS data collection cruise, and investigating permitting of seismic and multibeam data acquisition.

 

Sorlien

University of Southern California

075639

Building the SCEC 3D community fault model: Santa Barbara Channel and Santa Monica bay

2/1/02-1/31/03

This project, with graduate student Kris Broderick, is to provide digital structure-contour maps of faults to the SCEC community fault model (CFM). Maps constructed by Marc Kamerling and Sorlien have already been provided, including maps on the Oak Ridge fault, the offshore Pitas Point, North Channel, and Red Mountain faults in Santa Barbara Channel, and the Dume segment of the Santa Monica fault in Santa Monica Bay. We are preparing the digital version of maps on the San Pedro basin fault, the Malibu Coast-Santa Cruz Island fault, and the tip of the Channel Islands thrust, and will revise a subsurface map of the Hosgri fault. We will participate in discussions and workshops concerning alternate fault interpretations.

 

Sylvester

DOI/USGS

01HQAG0178

Structural mapping along the central Rancho Nuevo Creek and Madulce Peak Qu

7/1/01-6/30/02

As stated in the objectives, the funds allocated to this project were used to support Nate Onderdonk during the summer and fall of 2001.During this 6 month time period, Nate mapped the southern halves of the Rancho Nuevo and Madulce Peak quadrangles in the Los Padres National Forest at a scale of 1:24,000. This mapping resulted in a detailed description of structural relationships and the distribution of geologic units in the area. The most significant outcome was the development of a new interpretation of the western Big Pine and Pine Mountain faults as a single continuous north-dipping reverse fault. This interpretation resulted in a major revision of the regional structural framework and contributed to our understanding of deformation along the northern edge of the rotated western Transverse Ranges.

 

Tanimoto

NASA

NAG5-7981

Atmospheric excitation of planetary normal modes

1/1/99-12/31/01

Enigmatic earth's background oscillations were discovered in 1997.  Even when there are no earthquakes, the whole earth seems to be oscillating continuously.  One of the potential causes of these oscillations is an atmospheric effect; turbulent atmosphere,as we know it from winds and typhoons and hurricanes, may be applying pressure on the surface of the Earth continuously and exciting these oscillations.  This grant examined a potential application to future investigations on Mars.  In the near future, seismometers may be installed on the surface of Mars and if this atmospherically excited oscillations existed in Mars, we may be able to record oscillations and be able to infer the internal structure of Mars. Feasibility of such application was estimated quantitatively.  In Mars, expected amplitude of these oscillations are at most half of those observed in the Earth.

 

Tanimoto

UC-IGPP

Continous ffree oscillations and its application to palnetary seismology

02-1206

10/1/01-9/30/02

Earth's background oscillations consist of fundamental mode oscillations with period about 5 minutes.  The main question attacked by this grant was which atmospheric processes have the right frequencies and where they are acting in the earth. Atmospheric scientist, Doug ReVelle at Los Alamos, was the collaborator on this project.  This project was renewed and will continue in 2002-2003.

 

Tanimoto

National Science Foundation

EAR-9972855

Nature and cause of long period background oscillations

9/1/99-8/31/02

Basic characteristics of background oscillations were determined from broadband seismographs from all over the world.  Background oscillations are global phenomena and signals were seen at any quiet seismograph stations.  Theory for the atmospheric excitation was developed and fit to the seismic observation was attempted.  Data can be fit by the developed theory but theory contains two important parameters (spatial and temporal correlation) that are intrinsic to turbulence and are basically unknown at the moment.  Verdict for the atmospheric hypothesis is not in yet.  There is still a chance, perhaps a great chance, that ocean process may be the cause.