1/1/98 8/31/00 $60,000
American Chemical Society Petroleum Research Fund, 32624-AC8
High Resolution Sequence Stratigraphic Framework of a Tectonically Active Forearc Basin
Mesozoic rocks of the Baja California Peninsula form one of the best-exposed and most areally extensive, well preserved convergent margin complexes in the world.
Busby proposes that this convergent margin shows an evolutionary trend that is typical of arc systems facing large ocean basins: a progression from highly extensional through mildly extensional to compressional strain regimes.
This proposal focuses on the southernmost end of the Peninsular Ranges forearc basin complex of southern California and northern Baja California, Mexico, the Rosario embayment.
Busby suggests that the Peninsular Ranges forearc basin complex formed as forearc strike slip basins under a compressional convergent margin strain regime, where strong coupling promoted the development of strike slip faults during oblique subduction.
Strike slip basins are known to be the most tectonically active and complex basin type of all, characteristically showing very rapidly alternating subsidence, uplift and titling events of great magnitude.
This makes them ideal for the kind of detailed "tectono-stratigraphic analysis" that is proposed here.
Busby and a graduate student will spend 3 to 4 months in the field mapping the entire basin at a scale of 1:50,000 or better using aerial photographs, satellite imagery and topographic bases.
Packages of strata will then be dated using foraminifera, nannofossils, macrofossils and magnetostratigraphic data.
7/1/97 - 6/30/99 $24,300
UC Energy Institute, 08970725
Measurement of Natural Marine Hydrocarbon Seepage
Using an Atmospheric Tracer Method
Natural marine hydrocarbon seeps near Coal Oil Point, Santa Barbara County, CA, pollute the coastal ocean and regional atmosphere.
Chemical signatures from these seeps can be followed for 100s of kilometers away from the point.
Potentially, the most serious consequence of seepage is its relationship with the formation of ozone.
The seeps are significant sources of reactive organic gases (ROGs) which are precursors to ozone.
Although they are poorly constrained, estimates of the total flux of ROGs from these seeps are of the same order of magnitude as the total anthropogenic source in this county and may be substantially larger than the value currently used by the local air pollution control board.
It is critical for policy makers to have accurate estimates of all sources of ROGs including natural sources so that they can assess the likely impact of further economic development on air quality in Santa Barbara County and so they can develop realistic air quality goals.
Our project will attempt to quantify the total emission rate of ROGs to the local atmosphere by conducting atmospheric gas tracer experiments above an intense area of seepage at the eastern end of the Coal Oil Point seep field.
The results for these experiments will provide a calibration for high resolution digital sonar surveys (3.5 and 12 kHz) which determined the relative flux of hydrocarbons from the entire seep field.
Two tracer experiments were completed during May and June and a third experiment which will be conducted in conjunction with a new high resolution sonar survey is planned for late September.
This project is a part of on-going research which is focused on determining methods of quantifying natural marine seepage and identifying the effects of oil production on seepage rates.
9/1/95 - 8/31/98 $20,072
National Science Foundation, EAR-9506687
Petrologic Evolution of the Northern Eldorado Mountains, Southern Nevada
The lower Colorado River extensional corridor in southern Nevada, western Arizona, and southeastern California records in exquisite detail the volcanic and structural evolution of a failed propagating continental rift, making it an ideal natural laboratory to examine the interplay between continental extension and magmatism.
Large magnitude extension (i.
³ 100%) within this corridor is indicated by pervasive normal faulting and tilting of Miocene volcanic and sedimentary rocks, by unroofing of mid-crustal metamorphic and plutonic rocks, and by crustal thinning (from ~40-45 km to ~25-30 km).
For any given area within the corridor, 4-8 m.
of voluminous mafic to silicic volcanism is accompanied, in part, by regional extension.
The inception of volcanism preceded the inception of major extension, and distinct differences in pre-, syn-, and post-extensional eruptive volumes have been documented.
The Eldorado Mountains record a suppression of volcanism during and following high-magnitude extension which may be related to the effects of normal faulting in the shallow crust (Gans and Bohrson, 1998).
A petrologic investigation of the northern Eldorado Mountains is currently underway to document tectono-magmatic interactions in a continental rift.
Changes in major and trace element (~30 analyses) compositions of mafic volcanic rocks erupted prior to, during, and after large-magnitude extension indicate that there may be variations in the relative contributions of asthenosphere and lithosphere as extension waxes and wanes.
Trace element evidence suggests that pre- and syn-extensional magmas may be largely derived from the lithosphere, whereas post-extensional magmas appear to have a significant contribution from the asthenosphere.
Isotopic work (Sr, Nd, Pb) currently in progress indicates that the lithosphere has contributed extensively to most if not all of the lavas.
Documenting the relative contributions of crust, lithospheric mantle, and asthenospheric mantle is essential for understanding how the structure of the upper mantle and crust changes during high-magnitude extension.
National Science Foundation, EAR97-28643
Xenoliths from the North-Central Tibetan Plateau- INDEPTH III Geologic Team
During a geologic transect across the Qiangtang terrane, INDEPTH III geologists discovered xenoliths, the first reported from the Tibetan plateau, at three separate localities in the area of 34° 24'N, 89°14'E.
The host rocks are moderately porphyritic felsic lava flows interlayered with basaltic lava flows.
The relatively fresh trachyandesite to trachyte host rocks are characterized by high K2O (K2O/Na2O=1.5-2.0) and therefore belong to the shoshonitic series.
Phenocrysts include An30 plagioclase, An05Or56Ab36 sanidine, quartz, pargasite, and abundant phlogopite, monazite and apatite; the holocrystalline groundmass is dominated by sanidine, phlogopite, ilmenite, titaniferous magnetite, and apatite.
Whereas the basalts contain only extremely rare xenoliths, the more evolved flows contain readily visible mm- to cm-size xenoliths and xenocrysts.
The xenocrysts are chiefly sanidine, garnet, and quartz.
The most abundant xenoliths are granulite-facies rocks with garnet + enstatite + plagioclase + phlogopite + apatite + hercynite + monazite.
Less common are phlogopite websterite, phlogopite gabbronorite, garnet + plagioclase + tourmaline + quartz granulite, and augite + pargasite + plagioclase + monazite + apatite amphibolite.
Partitioning of Fe and Mg between coexisting augite and enstatite indicates xenolith equilibration temperatures of c.
1000°C, and Al partitioning between garnet and enstatite indicates pressures of 1.3-1.5 GPa, equivalent to extraction depths of c.
These calculated PT conditions are compatible with the presence of kyanite inclusions in garnet, which requires pressures >1.4 GPa at 1000°C.
Textural evidence of the decompression reaction, garnet (alm57prp36grs05sps03) + opx (4.8% Al2O3) + Na-cpx --> opx (7.6% Al2O3) + hercynite + magnetite + oligoclase, is widespread.
Volcanic rocks nearby have yielded ages of c.
1 and 8 Ma (Turner et al.
, 1997), suggesting that the xenolith-bearing flows were erupted since the Late Miocene.
Teleseismic P waves recorded in Tibet indicate that the crust of the Qiangtang terrane is c.
65 km thick (Owens and Zandt, 1997), implying that these xenoliths are samples of the lower crust.
6/1/95 - 6/30/99 $62,356
National Science Foundation, EAR-9526016
Quaternary Evolution of the Eastern California Shear Zone
between Latitudes 36 degrees and 39 degrees
Geologic mapping along the Towne Pass fault as well as surveying of topographic profiles, using a Leica Total Station, across the most recent fault scarp was completed.
The mapping indicates that the western end of the Towne Pass fault is an older normal fault; movement is Miocene to Pliocene in age and there is no evidence for Quaternary faulting.
Surveying of 3 beheaded stream channels along the Owens Valley fault was also completed.
The 2.4 m of vertical offset across the scarp and the 20 km long rupture was the result of a single earthquake event.
Diffusion erosion modeling, using a numerical technique, of the surveyed profiles indicates that the fault scarp formed, hence the earthquake occurred, 7-12 thousand years ago.
Moment magnitude associated with this earthquake is on the order of 6.7-6.9.
Work over the next year will focus on trenching studies along the Deep Springs and White Mountains fault zone.
4/1/96 - 3/31/99 $207,419
National Science Foundation, EAR-9526861
Geometry and Timing of Gneiss Dome Formation, Southern Tibet, China
This project combines field mapping, structural studies, metamorphic petrology, and geochronology to characterize and document the structural and tectonic evolution of gneiss domes in southern Tibet.
This project is being completed with the collaboration of geologists from the Institute of Geology, State Seismological Bureau, Beijing.
Last year we completed mapping of the Kangmar dome and this year our efforts focused on metamorphic petrology, U/Pb zircon geochronology, and Ar/Ar and fission track thermochronology of samples collected from this dome.
The results of these analytical studies indicate that the rocks in the Kangmar Dome were buried to depths of 23 km and heated to temperatures as high as 625
C and exhumed rapidly between ~15 Ma and 10 Ma.
These studies suggest that this gneiss dome is compressional in origin and formed simultaneously with the Southern Tibetan Detachment System.
In addition, this last spring we spent two months mapping, at 1:50,000 scale, the Majba Dome, which is located ~100 km to the west of the Kangmar Dome.
We mapped a sequence of Paleozoic sedimentary rocks that grade downward into high grade metamorphic rocks, orthogneisses, and migmatites.
We also identified two primary deformation events: (1) north-south compression resulting in open to isoclinal folds and superimposed on that (2) north-south extension resulting a domed mylonitic foliation and north-south stretching lineation.
In addition, we mapped two post-tectonic granites.
Numerous rock samples were collected for petrology, microscopic structural and kinematic analyses, U/Pb geochronology, and Ar/Ar and fission track thermochronology.
Preliminary U/Pb geochronology suggests that one of the post-tectonic granites is 14.5±0.
1 Ma and therefore the deformational fabrics are pre-Middle Miocene.
Work over the next year will concentrate on mineral separation for additional geochronology and thermochronology analyses, and compiling structural and field data.
8/15/97 - 7/31/99 $99,659
National Science Foundation, OPP-9615281
Collaborative Research: Air-Ground Study of Tectonics at the Boundary Between the Eastern Ross Embayment and Western Marie Byrd Land, Antarctica: Basement Geology and Structure, and Influences on West Antarctic Glaciation
Structure at the boundary between the Ross Embayment and wMBL may be a result of 1) Cenozoic extension on the eastern shoulder of the Ross Sea rift, or 2) uplift and crustal extension related to Neogene mantle plume activity in wMBL; or a combination of the two.
Faulting and volcanism, mountain uplift, and glacier downcutting appear to now be active in wMBL, where generally E-to-W-flowing outlet glaciers incise Paleozoic and Mesozoic bedrock, and deglaciated summits indicate a previous N-S glacial flow direction.
Our study will include aerogeophysics within a 400 x 400 km area using the NSF/OPP SOAR facility aircraft (Support Office for Aerogeophyscial Research) in the first season, now planned for 1998/99, combined with on-ground geology in this season and the following one.
Our rationale for a combined program is the complete coverage of crustal-scale structure from the airborne geophysics, and mountain-range and outcrop scales from the geologic field work.
During this past year we accomplished two items: 1) We purchased and set up a SPARC Ultra workstation that will be used for processing SOAR aerogeophysical data; 2) Luyendyk traveled to SOAR camp at Siple Dome Antarctica for familiarization and planning.
At Siple Dome Luyendyk worked with Don Blankenship and Jeff Williams of SOAR.
The survey boundaries and grid were finalized.
Plans were drawn up for the conduct of the survey in 1998/99.
Luyendyk was introduced to quality control procedures and saw the process of obtaining data.
Three flights were made into the survey region.
This next season (98/99) Luyendyk and Siddoway et al.
will be stationed at Clark Camp in the Ford Ranges, Marie Byrd Land.
Luyendyk will supervise the acquisition and QC for the aerogeophysics survey.
Siddoway will lead a trail party to explore the southern Ford Ranges in a collaborative project.
7/15/94 - 6/30/99 $175,536
National Science Foundation, OPP-9316712
Collaborative Research: Glacial Marine Stratigraphy in the Eastern Ross Sea and Western Marie Byrd Land, and Shallow Structure of the West Antarctic Rift
This is a collaborative project between Bruce Luyendyk at UCSB and Louis Bartek at the University of Alabama.
We conducted a marine geology and geophysics study of the Cenozoic glacial and tectonic history of western Marie Byrd Land (wMBL), West Antarctica, in the region of the eastern Ross Sea, Edward VII Peninsula, and the Ford Ranges.
The study region is located at the eastern edge of the Ross Sea and Ice Shelf.
The offshore work proposed here used the icebreaker
during January and February 1996.
No marine geophysical data were available from this large region.
We are concerned with these main problems:
What is the history of the West Antarctic ice sheet in this region?
How are West Antarctic rifting and the glacial history related?
The offshore survey obtained multibeam echo soundings, high resolution seismic reflection data, gravity and magnetic profiles, and bottom samples.
We also completed a site survey for the Cape Roberts Drilling Project in the western Ross Sea adjacent to the Transantarctic Mountains.
We contributed papers resulting from our preliminary studies to the Fall '97 national meeting of the American Geophysical Union (Hamilton et al.
, 1997; Kluiving et al.
, 1997; Luyendyk et al.
The major features in the eastern Ross Sea include the Edward VII Peninsula and the Colbeck Trough offshore.
The trough is up to 800-1000 m-deep, trends NNW for almost 100 kilometers, and is aligned with the Kiel Glacier onshore to the southeast.
Near the ice shelf front the trough is devoid of sediment.
Dredge hauls retrieved mylonitic rocks and cataclasites from the higher eastern wall.
Farther to the NNW the trough is cut through glacial marine sediments.
Multichannel seismic data here identify seismic stratigraphic sequences RSS1 and overlying RSS2 that have been previously mapped in the Ross Sea.
RSS1 and RSS2 are separated by a major unconformity (U6?).
NNE-SSW and NW-SE fault sets showing normal separation define grabens in acoustic basement holding RSS1.
RSS2 is not deformed and has internal layers that are tilted westward.
It is correlated with Late Oligocene and younger glacial marine sequence mapped elsewhere.
Modeling of gravity data locates major north-trending basins cut into acoustic basement.
Colbeck Trough does not cut the basement on the outer shelf.
The trough is a glacial erosion feature that follows pre-existing NNW-trending half-grabens.
We conclude that the continental margin in the eastern Ross Sea was deformed by several episodes of Late Cretaceous normal faulting and received syn-rift sedimentation (RSS1).
Denudation of western Marie Byrd Land during Late Cretaceous to Oligocene (?) time produced the West Antarctic Erosion Surface that may be present as one of the unconformities we mapped offshore (U6?).
Subsequently, the RSS2 sequence was deposited in Late Oligocene to Early Miocene time.
In Late Miocene to Recent time glaciers carved through northwest-trending grabens and RSS2 to form the Colbeck Trough and deposited glacial marine units onto the outer continental shelf.
Dips in RSS2 and younger units record westward tilt of the continental margin.
This regional tilting is interpreted as due to uplift of the plume-generated Marie Byrd Land dome to the east in Late Tertiary time.
During Palmer 9601 we completed a site survey for the Cape Roberts Drilling Project that includes over 250 km of multichannel (MCS) and high resolution single channel (SCS) seismic reflection.
The objective of the survey was to obtain seismic coverage offshore Cape Roberts that could be used to site drilling locations for the Cape Roberts Project and to later tie sedimentary sequences away from core holes.
Three fault arrays were identified offshore Cape Roberts: two sets of rift border faults striking NW and NNE, and a third set of ENE trending faults, oblique to the northerly trend of the rift basin.
Two igneous bodies, identified from magnetic anomalies and seismic data along the western margin of the basin, apparently resulted from magma ascending along pull-aparts where transfer faults cross-cut the main border fault on the west side of the Cape Roberts rift basin.
We propose that the activation of the rift border faults and subsequent subsidence of the Cape Roberts rift basin occurred during an episode of increased uplift in the TAM in Late Eocene time.
Our interpretations of seismic reflection data identify an angular unconformity between the gently east-dipping synrift unit (V4a) and the more moderately dipping pre-rift units (V4b and V5).
This sequence boundary is thought to correspond to the progressive opening of the Cape Roberts rift basin, associated with tilting and rotation of fault blocks along the eastern margin of the graben.
The underlying pre-rift sequences in-fill the Victoria Land basin to the east; however, these sequences gradually thin to the west towards Roberts Ridge, suggesting that the formation of the Cape Roberts rift basin postdates the major rifting phases in the Western Ross Sea that formed the larger and deeper Victoria Land Basin.
7/1/96 - 6/30/98 $23,500
UC Energy Institute, UCSB 08960643
Geophysical Investigation to Determine Impacts of Oil Production on Natural Hydrocarbon Seepage in the Santa Barbara Channel
Prolific natural hydrocarbon seepage offshore of Coal Oil Point in the Santa Barbara Channel, California contributes significant quantities of gaseous and liquid hydrocarbons to the local environment, and may also represent an important process at the global scale.
Insight into rates of seepage improves the understanding of local pollution from seeps and global seepage potential.
Constraining the volume of fluid migration in the crust associated with seepage is also relevant since such fluid movement can mark diagenetic processes and affect parameters of structural stability causing earthquake swarms.
The distribution of gaseous seepage offshore of Coal Oil point was mapped using 3.5 and 50 kHz sonar by imaging rising seep gas bubbles which act as acoustic scattering targets within the water column.
Examination of a series of mapped seep distributions reveals the following: (1) spatial location of seeps is principally controlled by structural features of the offshore geology, aligning with the east-west structural trends of anticline axes; (2) intensity of seepage emission correlates with structural relief and perhaps cross-cutting by faults; (3) both spatial distribution of seepage and volume emission rates vary over time; (4) drawing down of reservoir hydrocarbons and the reduction in reservoir pressure associated with offshore oil production is one contributing factor decreasing the extent of seepage and seep emission volumes; (5) areal extent of seep distribution within 13km
of platform Holly decreased from 0.9 to 0.4 km
and volumetric emission declined on the order of 50,000 m
/day between 1973 and 1995; (6) a current estimate of volumetric flux from seeps for the entire Coal Oil Point offshore area suggests emission is on the order of 1-2x10
of gas per day and 20,000-30,000 liters of oil.
National Science Foundation, OPP-9423534
U-Pb Analysis of Detrital Zircon in Late Proterozoic Rocks of Arctic Alaska: Implications for Tectonic Evolution of the Canada Basin
and Adjacent Polar Margins
The U/Pb detrital zircon study of Proterozoic metaclastic rocks in Arctic Alaska, designed to provide additional constraints on the tectonic evolution of the Canada Basin, initiated with a 3 week summer field program in 1995.
A total of 32 samples spanning the 1200 km strike length of the Brooks Range orogen were collected for detrital zircon analysis.
All of the samples have been processed by 6 undergraduate students supported by the REU grant.
In addition, the students were provided with instruction in mineral separation techniques as well as several informal seminars concerning geochronological methods.
To date, approximately 50 single zircon grains have been analyzed from 3 samples collected from the Proterozoic Nerukpuk Formation in the northeastern Brooks Range.
On the basis of the initial detrital zircon ages, which range from 1.0 to 3.1 Ga, it appears that Proterozoic clastic rocks in the Brooks Range received sediment from non- North American sources.
Additional analyses from the remaining samples will further understanding of the paleogeographic origin of northern Alaska and tectonic evolution of the Canada Basin.
4/17/97 - 10/16/98 $118,680
US Geological Survey, 1434HQ97GR0314
Acquisition of 3-D Subsurface Well Data & 3-D GIS
for the Ventura Basin, California
In the Ventura Basin, faults and folds accommodate high rates of oblique crustal strain and uplift rates exceed 10 mm/yr.
These faults represent a significant seismic hazard, yet much of what is 'known' about these faults and folds has been inferred from 2D balanced cross section models.
To test the reliability of these 2D models to predict 3D subsurface structure, we are evaluating a unique 3D dataset provided by the Ventura Basin Study Group (VBSG).
The VBSG study consists of 17 structure contour maps and 84 interlocking cross section data panels based on nearly 1200 correlated deep-penetration (1-5 km) wells.
Many of these wells drill active fault and fold structures associated with major fault systems, including the San Cayetano, Oak Ridge, and Santa Susana faults.
This integrated 3D study is based on wire-line logs, mud logs, paleontological reports, core analyses, and surface maps.
Each data panel typically ties in 4 directions to define the sides of a 3D data volume or cell.
The result is a 3D presentation of an enormous quantity of high-quality subsurface data that have been reconciled into a coherent geological interpretation.
Any 2D or 3D kinematic model of the basin and its associated fault and fold geometry must incorporate these data, if it is to be successful.
This project consists of three parts: 1) acquiring the VBSG subsurface study, 2) developing an on-line digital database of these and other data for the Ventura Basin, and 3) creation of three-dimensional models of the structures within the Ventura Basin.
This will help provide a basis for the understanding of the geometry, tectonic development, and seismic hazard of active fault structures in the Ventura Basin.
Steps 1 and 2 are now complete and Step 3 is underway.
The VBSG maps and cross sections have been digitally scanned and are now available to the public from our website at
Higher resolution versions of the digital images are also available for research purposes.
Once this stage is completed, the results of the VBSG study will be incorporated with other subsurface datasets and previous studies to create accurate 3D subsurface models for the active fault and fold structures in the Ventura Basin.
7/1/97 - 6/30/99 $38,177
US Geological Survey, 1434HQ7GR03173
Slip on the Channel Islands-Santa Monica Mountains Thrust:
Testing Models of Fault-Related Folding
During the past year, my students and I have continued work related to the tectonics and tectonic geomorphology of the Northern Channel Islands, supported by the National Earthquake Hazard Reduction Program (NEHRP) of the U.
and by a collaborative award from the National Science Foundation.
As discussed in last year's ICS Annual Report, the "thrust" of this research is using precisely-measured deformation of coastal terraces around the islands to infer the geometry and rates of slip on the reverse-fault structure that is believed to core the Northern Channel Islands trend.
Field work was all-but-completed during 1997-98, with final mapping of terraces and terrace deposits around Santa Cruz and Anacapa islands.
Finding the all-important terrace feature, the shoreline angle, continued to be a challenge in the field, but detailed work in virtually every canyon that incises the terraces has paid off.
Shoreline angles were measured or tightly bracketed at sites over broad areas around the islands.
Measurements were made using a laser total station tied to topographic benchmarks for elevation, and using a differentially-corrected (DGPS) positioning system for horizontal coordinates.
In addition, elevations of stripped terrace remnants are being assessed using a series of algorithms to filter the DEMs of the islands, combined with statistical techniques to apply best-fit surfaces to the terrace remnants.
All of the results from the DEMs are field-checked to rule out potential false signals from lithologic control or colluvial mantles.
Another challenge in this research is assigning ages to the different coastal-terrace levels.
In addition to previous uranium-series results from solitary corals, we have completed amino-acid-racemization analyses of shells from terrace-capping sediments, radiocarbon analyses of shells (combined with scanning electron microscopy to identify recrystallization or other potential problems), and strontium-isotope tests will be attempted on at least some of the samples.
The final stage of the research -- analysis of all field measurements, combined with age determinations, to give rates and patterns of deformation and to infer the geometry and slip rate on the underlying thrust fault(s) -- will be completed during the upcoming year.
3/1/97 - 2/28/99 $22,735
National Science Foundation, EAR-9706258
Collaborative Research: Testing Models of Fault-Related Folding,
Northern Channel Islands, California
Christopher Sorlien's part of the collaborative proposal has been to interpret the structure and stratigraphy of the shelf and slope between Santa Cruz-Anacapa islands and deep Santa Barbara basin.
He also spent almost two weeks in the field on the islands in support of Pinter and Scott's work on the coastal terraces and uplift and folding of the islands.
The sequence stratigraphy of the shelf has been interpreted north of Santa Cruz and Anacapa Islands.
Sequences have been correlated from the deep basin up onto the shelf at several locations.
We interpret that the tops of prograding sequences are controlled by sea level, and that the oldest of these sequences have subsided between 100 m to 200 m.
At least north of Santa Cruz Island, older sequences are more tilted than younger ones.
At least in the east, this subsidence is post-1 Ma, although the oldest sequence was deposited on an unconformity that had already tilted.
Uplift of the islands and subsidence of the shelf is a progressive north tilt that is not consistent with the published structural model.
Uplift of the islands, and probably of the Santa Monica Mountains, should be evaluated from a subsiding base-level, not from sea level.
2/15/97 - 8/14/98 $60,000
US Geological Survey, 1434HQ97GR03085
Fault Displacement and Fold Contraction Estimated by Unfolding of Quaternary Strata, Onshore and Offshore Ventura Basin, California
Christopher Sorlien, and Dr.
Kamerling and were funded by U.
Geological Survey National Earthquake Hazards Reduction Program (NEHRP) to study folding and faulting in the eastern Santa Barbara Channel and Ventura Basin using a three-dimensional map restoration technique.
A 1 Ma horizon offshore was mapped, and this map and the published onshore map were digitized.
A 3-D view was created, and the structure-contour map was unfolded and restored to an initial horizontal state.
A web page was created with Carmen Alex (
Published and unpublished cross sections were used to create a structure contour map of an ~1.8 Ma horizon through western onshore Ventura basin.
Industry seismic reflection data and well data were used to create a new structure-contour map of this horizon offshore.
This map of a deeper horizon will be restored if our proposed renewal is funded.
Previously, 3.5 km of post-1 Ma left slip and a similar amount of vertical motion was claimed for the Oak Ridge fault near Santa Paula based on an offset stratigraphic marker.
It is not possible to restore the 1 Ma horizon with this much left slip unless an unmapped fault cuts across Ventura basin near Santa Paula.
Without this fault, post-1 Ma left slip in this area is between 1 and 2 km, or half the published estimate.
Another NE-SW tear fault is required by our subsurface mapping near the Ventura River, and this fault may link slip on the Red Mountain fault to slip on the Padre Juan-Javon Canyon fault.
These faults may form important kinematic boundaries that could limit the rupture areas of future earthquakes.
Correlation of post-160 ka horizons dated at Ocean Drilling Program site 893 and the 1 Ma horizon shows that vertical motions across the offshore Oak Ridge fault and related folds have not changed in the last 1 Ma.
US Geological Survey, 1434HQ96GR02732
Strain Partitioning in Los Angeles-Ventura Region, Southern California: Evidence from Precise Leveling Across Active Folds and Faults
Ventura Avenue anticline is a geologically young, major fold that grew 4-5 mm/yr during Holocene time (Rockwell, et al.
Comparison of three first-order leveling surveys across the anticline, 1978 (NGS), 1991 (County of Ventura), 1997 (UCSB) indicate that the crest of the Ventura Avenue rose 20 mm between 1978 and 1991 and about another 10 mm between 1991 and 1997, for an annual rate of uplift of about 1.5 mm.
All of this has happened without the benefit of nearby earthquakes.
Between 1978 and 1991 no earthquakes > M2.0 were recorded anywhere close to the anticline, even though GPS measurements from 1988 to 1994 indicate horizontal shortening of 7 mm/yr across the entire Ventura basin.
By state law, furthermore, produced fluids must be replaced to mitigate potential subsidence, and comparison of two NGS levelings done shortly after the law went into effect in 1956 indicate that a re-injection program was successful in countering local subsidence (Buchanan-Banks, et al.
The aseismic growth of Ventura anticline provides permissive evidence to counter assumptions that folds only grow coseismically in this region, and that strain accumulation inferred from GPS measurements will be released only elastically in future, frequent, Northridge-type earthquakes, or infrequent, even larger shocks (Dolan et al.
This observation of aseismic fold growth is critical to understanding how regional strain may be partitioned between elastic and anelastic deformation.
If aseismic fold growth and possibly fault creep are occurring elsewhere in the greater Los Angeles area, thereby releasing some fraction of accumulated strain energy, then seismic hazard estimates for the Los Angeles region may be significantly different than inferred by Dolan et al (1995) based on a wholly elastic model.
Impending earthquakes may be smaller and/or less frequent, therefore, than maintained by those investigators.
See additional information at:
US Geological Survey, 1434HQ97GR03132
Investigation of Seismic and Aseismic Behavior of Active Fault Segments: Integration of UCSB Nearfield Geodetic Arrays
According to conclusions reached from recent GPS geodesy, more elastic strain energy is accumulating in the Los Angeles region than is being released by means of earthquakes, leading to the conclusion that the region may expect either more frequent Northridge 1994 size earthquakes in the future or less frequent but larger earthquakes (Dolan et al.
One explanation for the discrepant strain budget is that a "significant" proportion of that horizontal shortening strain is being released anelastically - slowly, inexorably by fault creep, folding, and regional uplift - although some investigators (Dolan et al.
, 1995) dismiss this possibility with precious little evidence.
This investigation seeks to test the hypothesis that the Transverse Ranges in southern California are rising anelastically as the partitioned response to measured north-south crustal shortening.
It is a relevant phenomenon for a NEHRP study, because if a large proportion of the regional strain is being released anelastically, then less is available for elastic release in earthquakes, meaning that the earthquake hazard is not as great for the greater Los Angeles area as some investigators have maintained.
We know the Transverse Ranges rise at the time of earthquakes, and based on our leveling in 1996/97, we think the Transverse Ranges also rise in interseismic time by anelastic deformation.
We think that a comparison of levelings across the ranges in 1998 when compared with previous levelings will reveal the place and rate of uplift since as early as 1934, when most of the main bench marks were installed.
We intend to resurvey two lines by precise leveling of two lines of existing bench marks across the Transverse Ranges - one along Hwy 33 from Ventura to Cuyama, and one in Cajon Pass from San Bernardino to Hesperia.
We shall make simultaneous GPS observations of almost all bench marks to integrate with the greater network of GPS bench marks in southern California.
These data and their subsequent analysis will link 60 years of leveling data with present and future GPS observations, and yield a 60 year record of vertical movement of two broad and different parts of the Transverse Ranges.
anticipate that we'll find the mountains have risen, then we shall model the data to understand how and why.
The importance of the test bears on balancing the strain budget in southern California - how the geodetically measured shortening is apportioned into stored elastic strain that is available for potential damaging earthquakes, and if and how much is released anelastically by creep, regional vertical uplift, and folding.
University of California Energy Institute, UCSB 08960644
Impacts of Oil Production on Natural Hydrocarbon Seepage in the
Santa Barbara Channel Determined by Fluid Dynamic Modeling of Dissolved Hydrocarbon Plumes
Natural oil and gas seeps offshore of Coal Oil Point in the Santa Barbara Channel release a significant amount of hydrocarbons (in the form of gas, oil and tar) into the environment.
Because the seeps are in relatively shallow water only part of the gas dissolves in the ocean while the rest is released into the atmosphere where it contributes to ozone formation.
Sonar surveys by the Institute for Crustal Studies determined the size and location of the seep field and have shown that the amount of gas (primarily methane) being released into the atmosphere is 105 m3 per day.
Analyses of the water during the 1995 and 1996 cruises found the peak dissolved methane concentrations of order 1000 nmol/l.
In order to verify the magnitude of the gas flux, I have used the Princeton Ocean Model to simulate the water flow in the Santa Barbara Channel.
The computational domain extends from shore to the channel islands and from Anacapa Island in the east to Point Conception in the west.
The numerical grid consists of 105 columns by 43 rows of control volumes.
There are 10 control volumes from sea surface to bottom scaled in size based on the water depth.
Turbulence, realistic bathymetry, temperature and salinity variations, tidal forces, and wind stresses are included in the simulations.
Dissolved hydrocarbons are represented by a passive tracer.
The simulations are driven by both wind stresses (constant northwesterly wind over the entire domain) and tidal fluctuations in the water depth.
The simulations produce a predominantly westward flow close to shore in agreement with available oceanographic data.
In order to obtain dissolved methane concentrations consistent with our analyses, the amount of methane going into solution must be around 5 x 104 m3 per day.
7/1/97 - 6/30/99
University of California Energy Institute, UCSB 08970726
Direct Measurement of Natural Hydrocarbon Seepage Off Coal Oil Point Near Santa Barbara, CA
A significant source of air pollution for Santa Barbara County is the natural seepage of hydrocarbons off Coal Oil Point near Santa Barbara, CA.
The seepage contributes to air pollution in the county because the hydrocarbons contain reactive organic gases (ROGs).
ROGs are precursors in forming ozone which is a significant air pollutant for the county.
The hydrocarbons seep into the water column from the sea floor as gaseous emissions and as liquid oil.
We are using sonar surveys to map these bubble emissions and to quantify emission rates.
We have found that the gaseous seep emissions may equal the ROGs emitted by all mobile sources in the county.
The objective of this research is to measure directly the seep gas emissions to the atmosphere with a new, independent technique.
It is critical to policy makers in Santa Barbara county to have accurate inventories of all sources of ROGs.
This research will contribute to this by improving estimates of natural hydrocarbon seepage.
It will also help policy makers evaluate the effects of offshore oil production in the Santa Barbara Channel.