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SURE Intern Projects, Summer 2007
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Mentor: Andy Barth, Indiana University~Purdue University, Indianapolis, IN
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Developing a Three-Dimensional Geophysical Model of the Crust in the Transverse Ranges of Southern California
Improving models of crustal structure is necessary to accurate calculation of earthquake hypocenters, and to understanding how crustal architecture influenced the development of faults in southern California. The summer intern will use tilted crustal cross sections in the Transverse Ranges to build models of Southern California crustal structure. The project will begin with field work along sampling transects through tilted crustal sections in the San Gabriel Mountains and Little San Bernardino Mountains, describing and sampling key rock units. Following fieldwork, the intern will be responsible for carrying out of laboratory measurements of rock density, magnetic susceptibility, and radiogenic heat production, and use computer modelling to construct a model regional crustal lithologic column across several fault blocks. The summer intern should have a background in petrology and/or geochemistry, and enjoy field work in mountainous terrain. Experience in geographic information sytems (GIS) would be a plus. This project will contribute to the SCEC Unified Structural Representation project in the development of a 3D model of Earth structure in southern California.
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Mentors: Eric M. Dunham and James R. Rice, Harvard University, Cambridge, MA
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Earthquake Ruptures on Rough Faults
While faults are known to have irregular surfaces, almost all models begin with the assumption of perfect planarity. Slip between rough surfaces induces heterogeneous stress changes, in particular alterations of the normal stress that might lead to opening. Opening has been observed in the foam-rubber laboratory experiments of Brune and Anooshehpoor at UNR, and the resulting "chatter" between the fault walls during dynamic slip has been suggested to explain pulverized rocks observed near faults. Recent LIDAR measurements place constraints on the roughness spectrum of actual faults. The objective of this project is to explore the influence of fault topography on dynamic ruptures. A first step will be the development of a computational method to handle rough faults. The approach is to define a mesh (in "physical space") comprised of irregularly spaced cells that precisely tracks the fault surface. Next, a coordinate transformation is executed that maps the mesh from physical space to a regularly spaced Cartesian mesh in so-called "logical space." The governing equations (the elasticity equation off of the fault and the friction law on the fault) are likewise altered by the change of variables, but the permitted class of coordinate transformations ensures that the elasticity equation remains hyperbolic. The resulting equations are solved in logical space, either with finite-difference or finite-volume methods. Should we find that normal stresses do locally become tensile, then the process of fault opening will require a careful study. Here the focus will be poroelastic effects, since opening between two fluid-infiltrated solids presumably induces a suction that will draw fluid out of the rock matrix and into the opening between the fault walls. Once this void fills with fluid, then abrupt closure is rendered more difficult. A coupled fluid-poroelastic solid problem can be defined to address these issues, and any results incorporated into our models. The project requires knowledge of multivariable calculus, partial differential equations, and linear algebra, and of beginning college-level physics at a level appropriate for physics concentrators. The study will be supervised on a day-by-day basis by Dr. Eric M. Dunham, now Reginald A. Daly Postdoctoral Fellow in the Department of Earth and Planetary Sciences at Harvard, and will have overall supervision by Prof James R. Rice, a member of that same department.
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Mentor: James P. Evans, Utah State University, Logan, UT
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Analysis of Faulted Rocks From Core
Surface exposures of fault-related rocks provide important clues into the processes of faulting, but core provides an even richer record of
the deformation and fluid flow associated with earthquakes. We hope
to work on two sets of core from the San Andreas
fault. Core from the Cajon pass well, drilled in the 1980s, and
core from the San Andreas Fault Observatory at Depth (SAFOD) will be
studied to help determine the deformation processes in and near
seismogenic faults. Core from SAFOD is scheduled to be acquired in
June-July 2007, and if recovery is good, the intern can participate
in the initial description of core as it is acquired at the drill
site. Cajon Pass core is stored at the USGS core lab in Denver, CO.
In addition to core description, interns can participate in
microstructural and geochemical studies. Interns will work with M.
S. and PhD students as well as the SCEC mentor. If SAFOD onsite work
is chosen, then collaboration with USGS, university faculty, and
students from various institutions will also be available. Students
who work onsite at SAFOD would be part of one of three 8-person teams
that work 8 hr shifts around the clock while core is acquired.
Locations for the projects are Denver, Co (1-2 weeks, housing
provided); Logan, Utah; southern California (field work for 1
week), and SAFOD site (Parkfield, CA). Mid-May-end of August time
frame. Prefer students majoring in geology or geophysics with an
undergraduate course in structural geology.
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Mentor: David Bowman, California State University, Fullerton, CA
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Formulation and Evaluation of Fault- and Alarm- Based Earthquake Prediction Algorithms
The objective of this project is to generate fault-based earthquake forecasts for California. As in intern for this project, you will create computer models predicting the stress field before potential ("scenario") earthquakes on the San Andreas system. These stress fields will then be compared to observed earthquake catalogs to assess the hazard posed by each scenario. Scenarios will be submitted to SCEC's new Collaboratory for the Study of Earthquake Predictability. By participating in this project, you will gain familiarity with a number of topics including static (Coulomb) stress transfer modeling, seismic hazard analysis, and the analysis of earthquake catalogs. No previous modeling experience is needed; the modeling software employs an easy-to-use graphical interface. The work will be conducted at Cal State Fullerton and will require a junior or senior level student who has had at least one course in structural geology or geophysics.
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Mentor: Elizabeth Cochran, University of California, Riverside, CA
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Damage Zone Structure Along the Calico Fault
Fault damage zones are an active area of study intrinsic to our knowledge of earthquake nucleation and propagation. Recent InSAR and seismic studies highlight the complex nature of these damage zones and much is still unknown about their three-dimensional structure and evolution through time. To that end, seismic data were collected along the Calico fault in the eastern California shear zone from June to November, 2006, in a collaborative effort by scientists from several southern California universities. The SCEC/SURE intern will be responsible for picking seismic arrivals from the 6 month long data set of local, regional, and teleseismic earthquakes. These travel-time picks will then be used in a tomographic inversion to determine the 3D structure of the damage zone along the Calico fault. The intern is expected to have working knowledge of UNIX, a willingness to learn seismic analysis software, and knowledge of programming. Knowledge of Fortran is preferred, but any programming will be helpful.
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Mentor: Zhigang Peng, Georgia Institute of Technology, Atlanta, GA
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Systematic Analysis of Crustal Anisotropy around the Los Angeles Basin
Understanding active fault structures and stress conditions around the Los Angeles (LA) basin is crucial for addressing seismic hazards in this region. Seismic shear waves propagating inside the anisotropic upper crust are expected to split into two orthogonally polarized waves with different velocities. This phenomenon is analogous to optical birefringence, and is generally termed shear wave splitting (SWS). SWS measured from local earthquake source provides an effective tool for analyzing regional stress state in the upper crust and near-fault anisotropic structures. The objective of this project is to obtain a complete anisotropy map around the LA basin, investigate spatio-temporal patterns (such as depth extent, relation to known fault structures, and temporal changes associated with major earthquake occurrence), and identify causing mechanisms (stress-induced versus structure-controlled anisotropy). The summer intern will be responsible for downloading available seismic waveform data from SCEDC and IRIS data center and organizing them, applying a recent developed computer code to automatically measure splitting parameters, and developing a product on crustal anisotropy in this region that is openly available to the SCEC community. The summer intern needs to have a basic knowledge in UNIX and geophysics, and is willing to work with large seismic waveform dataset. The work will be conducted at Georgia Tech.
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Mentor: Lisa Grant Ludwig, University of California, Irvine, CA
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Project 1: Paleoseismic Study of the San Andreas Fault in the Carrizo Plain just west of Taft, CA
The San Andreas Fault is the most significant source of seismic hazard in California. The clues to its future behavior lie in the data that indicate the chronology and magnitude of earthquakes that have occurred during the past few thousand years. These data can only be collected in the field. This summer, we will be collecting paleoseismological data along the Carrizo section of the San Andreas Fault, just west of Taft, CA. We will be excavating 2 new trenches in the fault zone in an attempt to lengthen the record of earthquakes in the Carrizo Plain. The field work will expose you to all the components of a paleoseismic study, including site selection, digital photo taking, logging and organic material collection for radiocarbon dating. Office work will include data compilation and drafting logs on a computer. If you have taken a basic geology course, such as Natural Hazards or Introduction to Geology, and feel comfortable with computers, this may be the summer project for you. You will need to be available by the end of May or early June.
Project 2: Using Precariously Balanced Rocks to Place Constraints on Ground Shaking Along the Southern San Andreas Fault
Precariously balanced rocks, common throughout the desert southwest, and near the San Andreas Fault, can place constraints on the ground shaking (important in designing buildings to resist earthquakes) caused by earthquakes that occur along the southern San Andreas Fault. The project will involve sample detection and possibly analysis to determine the length of time that these rocks have been precariously balanced; and help in constucting a GIS database. If you have taken a basic geology course, such as Natural Hazards or Introduction to Geology, feel comfortable with computers, and are able to work without much daily direction, this may be the summer project for you.
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Mentor: Ze'ev Reches, University of Oklahoma, OK
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Characterization of gouge powder from rupture-zone of recent earthquakes and rupture-zones developed in laboratory experiments
Gouge is an incohesive, fine grain powder that is found in all active fault zones in the brittle crust. As gouge formation is attributed to slip during earthquakes and to fault creep, gouge properties may serve as a powerful key to understanding earthquake energy balance, slip instability, creep controlling parameters, and frictional melt. Recent analyses of gouge properties have provided a range of results, yet these results may differ from one study to other probably due to analytical techniques, different site or interpretation of field relations. The central objective of this project is to analyze the properties of siliceous gouge samples from rupture-zones of recent earthquakes that will be collected at focal depth, as well as fresh gouge that formed in rock mechanics experiments. The samples will be analyzed in a few techniques: laser particle size analyzer, SEM, TEM, electron- microprobe, and BET. We think that this multi-technique approach will clarify the main characteristics of earthquake gouge powder. The research will be conducted in the University of Oklahoma, Norman, Oklahoma. The intern will test gouge properties in a range of laboratory techniques (listed above) under the supervision and collaboration of the responsible faculty and technicians in University of Oklahoma. It is anticipated that the intern had some experience in laboratory work (e.g., thin-section analysis, introduction to chemistry lab).
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Mentor: Doug Yule, California State University, Northridge, CA
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Paleoseismology of Main Frontal Thrust, Nepal
This research focuses on results from a trench site in far-western Nepal that has unearthed possible evidence of the Great June 6, 1505 earthquake, the largest earthquake to affect the Himalaya in the past 500 years. A SCEC intern would assist Dr. Doug Yule and his graduate students in their ongoing interpretation of the results from field work completed in the Fall of 2005 and 2006. Tasks would include (1) learning pertinent GIS to compile a 3D image of the trench site, (2) completing photomosaics of photographs taken of the trench walls, (3) researching the historic record from 1505 in northern India and southern Tibet, and (4) interpreting the geologic evidence from the trench site for this massive earthquake. The ideal intern would have some experience with GIS and would have taken courses in structural geology and stratigraphy and sedimentation.
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Mentor: Susanne Janecke, Utah State University, Logan, UT
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Mapping the Structural Complexities of Active Faults in Southern California
This project is certain to document and map previously unknown active faults. We will investigate the structural complexity of fault traces along the San Jacinto, San Felipe, and Earthquake Valley strike-slip fault zones, and learn about the wide range of linkages between active faults. The intern will build a digital map database of fault traces in Anza Borrego State Park, southern California, using many different data sets. Orthographic images, Landsat data, aerial photographs, InSar, seismic data sets, magnetic, and gravity data will all contribute to locating known and unknown faults. LIDAR data might be incorporated. Remote images will be the main source of data but these findings can be checked and calibrated using prior geologic maps and unpublished geologic mapping by Dr. Susanne Janecke's research group (where available). It is hoped that this effort will improve the Quaternary map database of the USGS (http://earthquake.usgs.gov/regional/qfaults) for southern California. Preliminary analysis already shows many omissions of active faults in this database. Internship prerequisites include being a geology major with structural geology and geomorphic coursework (preferred). Familiarity with graphic programs such as Adobe Illustrator is useful but not required. The research will take place in beautiful Logan, Utah, at the Utah State University.
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Mentor: James Dolan, University of Southern California, Los Angeles, CA
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Project 1: Defining Holocene Activity of the Compton Blind-Thrust Fault, Los Angeles Basin, California
One of the most exciting recent developments in seismic hazard assessment in Southern California has been the recognition of several large blind thrust faults directly beneath metropolitan Los Angeles. One of these blind thrust faults, the Compton thrust fault, was originally identified by Shaw and Suppe (1996). This large fault extends northwest-southeast for 40 km along the western edge of the Los Angeles basin. Seismic reflection data define a growth fault-bend fold associated with the base of the thrust ramp and, along with well data, reveal compelling evidence for its Pliocene and Pleistocene activity (Shaw and Suppe, 1996), but its current state of activity has been the subject of intense debate within the SCEC community. We recently used SCEC funds to acquire new, high-resolution seismic reflection profiles across the upward projection of the locus of folding above the base of the blind thrust ramp. These new observations demonstrate that the folding observed on oil industry profiles extends upwards to depths of less than 21 m, suggesting that this large fault is active and capable of generating destructive earthquakes directly beneath metropolitan Los Angeles. In this study we will collect basic information to determine the recent slip rate of the fault, displacements and ages of ancient earthquakes generated by the Compton thrust. In order to do this we will acquire a transect of eight, 25-35-m-deep, continuously cored boreholes drilled directly into the high-resolution seismic reflection profiles. Continuous cores collected during the drilling will allow us to correlate strata between boreholes as well as to collect detrital charcoal and organic-rich sedimentary layers for radiocarbon dating. The SCEC intern will be involved in all aspects of data acquisition, including the siting of boreholes, logging of cores, preparation of stratigraphic cross-sections, collection of carbon for dating, and surveying the field area. A student with some knowledge of sedimentology and structural geology would be preferred.
Project 2: Testing the Earthquake Clustering Hypothesis for the Eastern California Shear Zone with Paleo-Earthquake Ages and Displacements on the Calico Fault
Synthesis of paleoseismic data from the central Mojave Desert portion of the Eastern California shear zone (ECSZ) supports that notion that earthquakes recur in clusters across this portion of the southern California fault system (Rockwell et al. 2000).
The Calico fault is the longest and fastest-slipping dextral fault within the Mojave ECSZ (Oskin et al. 2006a, 2006b) and thus presents an ideal candidate to test the strength of the earthquake clustering hypothesis. The fault is embedded between the traces of the 1992 Landers and 1999 Hector Mine earthquake ruptures and centrally is located within the portion of the Mojave ECSZ where clustering was documented by Rockwell et al. (2000). Nothing is known about the rupture history of the Calico fault. In this study we will document the paleoseismicity of the Calico fault to test its behavior within the context of regional earthquake clusters identified by Rockwell et al. (2000). This effort will test three alternative hypotheses for the relationship of regional earthquake clusters to the rupture history of the Calico fault:
- The timing of rupture events on the Calico fault is strongly modulated by regional earthquake clusters. Faster slip on the Calico fault is accommodated by either (a) larger earthquakes or (b) multiple events during each clustering period.
- The timing of rupture events on the Calico fault is weakly modulated by regional earthquake clusters. Earthquakes occur on the Calico fault during each clustering period, but additional earthquakes occur between these periods.
- The timing of rupture events on the Calico fault is not modulated by regional earthquake clusters. There is no statistically significant higher probability that earthquakes occurred on the Calico fault during regional earthquake clustering periods.
In this study we will collect basic information to determine the ages and displacements of Holocene earthquakes generated by the Calico fault. We will excavate a series of paleoseismologic trenches across the fault trace along a dry lake bed east of Barstow, California. In addition to detailed mapping of the playa stratigraphy and fault-related structures formed during ancient earthquakes, we will collect both charcoal samples for radiocarbon samples and samples for optically stimulated luminescence (OSL) dating. The SCEC intern will be involved in all aspects of data acquisition, including the siting, excavation, and mapping of trenches, collection of geochronologic samples, surveying the field area, and mapping nearby portions of the fault trace to determine recent geomorphic offsets along the Calico fault (i.e., "real" field geology! :-). A student with some knowledge of structural geology and sedimentology would be preferred.
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Mentor: David Oglesby, University of California, Riverside
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Dynamic Models of Earthquakes and Tsunamis
For a 2007 Summer Undergraduate Research Experience project, I propose to investigate how the earthquake process affects the generation and propagation of tsunamis. We will construct and run computer models of tsunamigenic earthquakes and then use these models as inputs to computerized tsunami models. We will study how the geometry of the fault and the distribution of stress and frictional properties on the fault affect both the generation of tsunamis and the run-up of the tsunami on nearby land. The results will have implications for tsunami hazard in Southern California and worldwide. The successful intern will have some prior experience in programming and a basic knowledge of physics, although prior experience in numerical modeling is not necessary. The intern will aid in the setup of numerical models, and will take the lead in running these models and visualizing the results. We expect the results to culminate in a poster at the 2007 SCEC Annual Meeting, and then a peer-reviewed research paper. Research will take place at UC Riverside, with a possible short trip up to the USGS, Menlo Park.
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Mentor: Harry Green, University of California, Riverside
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A Test of the Frictional Limit in Subduction Zones
For a 2007 Summer Undergraduate Research Experience project, I propose to investigate in the laboratory the transition from frictional sliding on pre-existing faults to the creation of new faults due to dehydration embrittlement in subduction zones. Recently, my colleagues and I have demonstrated that pre-existing faults in serpentinized peridotite can be reactivated to pressures as high as 6 GPa and temperatures as high as 600 degrees C but that if the dehydration temperature of serpentinite is reached, such pre-existing faults are not reactivated; they are abandoned in favor of creation of new faults. For this Research Experience project, we will measure the stresses necessary to reactivate such pre-existing faults as a function of pressure and determine the minimum stress required for dehydration-embrittlement of antigorite serpentine. The successful intern will have some prior experience in examining rocks in thin section. Prior experience with experimental rock deformation would be advantageous but is not necessary. Following necessary instruction about specimen preparation and machinery operation, the intern will prepare materials for experimentation and will perform the experiments him/herself. We expect the results to culminate in a poster at the 2007 SCEC Annual Meeting, and then a peer-reviewed research paper. Research will take place at UC Riverside, with a possible short trip to the Advanced Photon Source (Chicago) or the National Synchrotron Light Source (Long Island, NY) for experiments interrogated in situ at high pressure and temperature by X-ray diffraction and imaging.
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Mentors: James Dieterich and David Oglesby, University of California, Riverside
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A Tests of Two Earthquake Modeling Methods
For a 2007 Summer Undergraduate Research Experience project, we propose to compare properties of earthquake ruptures generated by two very different computer codes. The first is a finite element method which solves the fully dynamic equations of motion on the fault and in the surrounding medium. The second is a quasi-static model in which displacement on faults is resisted by friction described by laboratory-derived rate-and-state-dependent constitutive relations. The latter model is mostly aimed at capturing the long-term interactions between earthquakes on different faults, and so the dynamic portion of the rupture process is modeled crudely with a fixed seismic slip velocity (whose magnitude is determined by simple radiation damping arguments). Partly because of this approximation, the quasi-static model takes several orders of magnitude less computer time to simulate a large earthquake than does the fully dynamic model. However, the quasi-static model does produce rupture scenarios that are, in many ways, reasonable. We will investigate how various elements of the models (e.g. pre-existing stress state, fault geometry) affect various aspects of the simulated ruptures (e.g. rupture velocity, ability to propagate past geometric complexities such as bends and stepovers) in both models to assess to what extent the simpler, faster quasi-static model captures the physics of the fully dynamic one. The successful intern will have some prior experience in programming and a basic knowledge of physics, although prior experience in numerical modeling is not necessary. The intern will aid in the setup of numerical models, and will take the lead in running these models and visualizing the results. We expect the results to culminate in a poster at the 2007 SCEC Annual Meeting, and then a peer-reviewed research paper. Research will take place at UC Riverside.
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For more information contact:
SCEC Education Programs
Office of Experiential Learning & Career Advancement
internships@scec.org
213-821-6340
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Southern California Earthquake Center
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