2000 Research Projects


Project Description: The main project I am interested in is the Kidzone at the Riverside County Children's Museum. My belief is that all the scientific research in the world is useless if it is not shared with others and I have learned that one of the most effective ways of sharing information with a large number of people is through a museum. Kidzone is a wonderful idea that will teach not only children, but adults, too, about earthquakes and how the earth moves and changes. I would like to be a part of making sure the exhibits at Kidzone are not only fun, but serve to get the information across to the public. I am also interested in assisting with the Seismic Sleuths project for the same reasons I am interested in the Kidzone project. I have read up on the project and it looks like a wonderful way to get earthquake information through to middle school and high school children.
Intern(s): Kathryn Van Roosendaal

Robert de Groot, University of Southern California

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Constraints on the SCEC 3D Velocity Model from Gravity Data: Two-Dimensional Gravity Modeling of the Central and Western Transverse Ranges in the Los Angeles Region

Project Description: The purpose of this work is to develop a regional gravity model based on version 2 of the SCEC 3D velocity model by providing an independent geophysical constraint on seismic tomography. This work builds on results summarized in the 1999 Annual Report by Roy and Clayton, which show that gravity data is an important tool for calibrating/constraining the SCEC 3D velocity model. Using crustal tomographic models (which are models of how P-wave or S-wave velocities vary as a function of position in the crust), simple empirical scaling relations will be used to derive densities as a function of position (Vp scales linearly roughly with density). Then density structures for a given region will be used to predict how the acceleration due to gravity varies over the region. Detailed data on gravity variations in the LA Basin and Transverse Ranges will be compared to the predicted gravity field. Previous work by Roy and Clayton for the preliminary version of the SCEC 3-D velocity model (version 1) found that in general the seismic tomography is consistent with the gravity, but with some discrepancies such as in the representation of the regional velocity (density) contrast between the LA Basin and the Transverse Ranges. The first part of this proposed work is to develop a regional gravity model based on version 2 of the SCEC 3D model. Additionally, the geometry of the LA Basin is not correctly represented in the SCEC velocity model, possibly due to lack of resolution in the near shore and offshore western margin of the basin. This region will be better defined by including some offshore and near shore industry seismic and borehole data and to derive empirical density-velocity scaling relations.
Intern(s): Nancy Natek

Mousumi Roy, University of New Mexico

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Array Analysis of Hector Mines Aftershocks to Identify Trapped Waves

Project Description: The problem is to investigate the source of fault zone trapped waves from aftershocks of the Hector Mines earthquake. Hypothesis: When an earthquake occurs within a fault, it generates longer period waves that arrive after the direct S wave. These waves are generated by the lower velocities that characterize the fault zone. Methods Seismic waves from the aftershocks of the Hector Mines earthquake will be analyzed based on recordings made by the SCEC southern Bouillon Wash array. Array analysis will determine the direction and phase velocity of the Fault Zone Trapped Waves (FZTW). Comparison between the directions and phase velocities of the FZTW and the direct S waves will determine whether FZTW originated in the fault zone or in the near surface materials beneath the instruments. Recordings from earthquakes that have originated both on and off the fault will be used to test our hypothesis. Array analysis will be applied to the seismograms using the LLNL Seismic Analysis Code.
Intern(s): Marie Ammerman

Ralph Archuleta, University of California, Santa Barbara

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Hector Mine: Postseismic Deformation from ERS InSAR

Project Description: In this project, I will monitor crustal deformation along a southern section of the San Andreas fault, particularly in the Mecca Hills and Indio areas of Southern California, using near-real-time interferometry. This new type of monitoring system provides more precise measurements of small-scale deformation compared to the current system of using a relatively coarse distribution of GPS monitors. In the near future, the formation of interferograms on a regular basis will allow scientists to observe increasing rates of strain and thus issue warnings of faults with high breakage (earthquake?) potential. Utilizing plans from David Sandwell‚s SCEC 2000 Proposal of "Near-Real-Time Interferometry of Southern California," as well as existing sources, I will investigate two questions involved with crustal deformation: (1) Is significant interseismic strain concentrated within a 4 km region of the fault? (2) Are there significant variations in the amount of strain along the fault? Hopefully, with the methods delineated below, I will develop a set of conclusive results. In completing this project, I will work at the Scripps Institution of Oceanography satellite ground station to capture synthetic aperture radar data (SAR) from the ERS-2 spacecraft (European Space Agency) when it flies along track 356. Track 356 crosses the region of the San Andreas fault containing Mecca Hills and Indio. Soon after each of the three or four flights along track 356 during the internship period, I will extract a frame of data from the respective flight that matches a frame from the WInSAR (Western North America InSAR) data archive. With the two frames of data, an interferogram will be created. Once the interferogram is available, I will use it to measure the profiles of strain across the fault in the study area. At this point, analysis of the profiles is necessary, whereupon I can interpret my observations. Also within this project, I hope to publish the current interferograms on the web on a consistent basis. The materials I will need are a computer workstation and a satellite ground station, both of which are available on the SIO campus. At some point in the project, I may take a trip to the actual location of make observations.
Intern(s): Allison Jacobs

David Sandwell, University of California, San Diego

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Pressure solution slip-faulting associated with the Quatal thrust fault

Project Description:The role aseismic deformation plays in the accommodation of strain associated with seismogenic faults is poorly understood. SCEC scientists Jan Vermilye and Leonardo Seeber have proposed a temporal model for the aseismic accommodation of shortening strains associated with the San Cayetano fault. I would like to help test the generality of this model by doing similar research on the Quatal fault. My role in this project will be to carry out stress and strain analyses for small pressure solution slip-faults in the damage zone surrounding the Quatal fault. I will collect kinematic data in the field, including fault strike, dip, rake magnitude of displacement, and sense of slip. The equipment necessary for this work is available from our departmental field supplies. I will analyze the collected data with a computer available in our department and three programs provided by Dr. Vermilye.
Intern(s): Kevin Mass

Jan Vermilye, Whittier College

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Three-dimensional analysis of the earthquake record on the San Andreas fault near Banning, California.

Project Description: My project will complement part of a larger study that explores the earthquake history of the San Andreas fault system near Banning, California. I hope to create a three-dimensional fence diagram of the area using the information of previously logged trenches and new trenches that will be opened this summer. Once familiar with the site stratigraphy, I will build a fence diagram using key structural and stratigraphic features, including faults, folds, marker beds, and event horizons. The relative positions of these features can be surveyed using a laser theodolite total station. These data will then be plotted using GIS software (Arcview or other equivalent software) to create the fence diagram. I will also make hand drawn logs and photo mosaics to show the key relationships. The fence diagram will provide a basis for approximating the shape of event horizons. The geometry of the paleo-surface can be constrained by extrapolating the event horizons between trenchcrops based on the available structural and stratigraphic information. A 3D approximation of each event horizon can show how the ground changed relative to each earthquake event going back in time. Once this is done we can estimate how much deformation occurred during the paleo-seismic events. This information will help constrain the magnitude of the earthquakes that rupture through the Burro Flats site. I anticipate spending 5-6 weeks in the field mapping and surveying the trenches, and ~5-6 weeks preparing the 3D fence diagram. Funding for fieldwork this summer has been awarded to Yule. Computer labs at Caltech and CSUN will be used to prepare the report and draft the diagrams.
Intern(s): Clay Stevens

Doug Yule, California State University, Northridge

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Refinement of near-surface P and S velocities in the SCEC 3D velocity model using 2D waveform modeling

Project Description: Using the tomographic inversion method of Hole (1992), we processed existing active-source industry data to create three P wave velocity profiles and an S wave velocity profile at 50 m pixel resolution for the upper 500 m of crust in the Northridge epicentral region of the San Fernando Valley (SFV). We found slow P wave velocities ranging from 0.9 to 2.6 km/s, S wave velocities ranging from 300 to 900 m/s, and a variable Poisson ratio ranging from 0.2 at the surface to greater than 0.4 just beneath it. Our profiles provide a valuable constraint on the SCEC 3D velocity model in the SFV where the near-surface S wave velocity, a critical parameter for accurate prediction of strong ground motion, is mostly indirectly controlled and in many areas not well constrained. We propose to compare the accuracy of the seismic response of the SCEC 3D velocity model against that for our profiles, in terms of amplitude and travel time. We define a SCEC summer internship project that will use 2D and 3D finite-difference modeling and Northridge aftershock data to test the accuracy of travel times computed by the SCEC velocity model in the SFV against those obtained from high-resolution 2D profiles of P and S wave velocities. In addition, we will use the profiles to attempt to constrain the quality factor (Q), separately for P and S waves, in the near-surface material using an accurate visco-elastic finite-difference modeling approach. Q is currently not included in the SCEC velocity model, despite of its critical importance for ground motion modeling. The outcome of this study may help improve the accuracy of the SCEC velocity model, and, therefore, future strong ground motion estimations in the SFV. The projects strongly complement the efforts within SCEC working groups B (Strong Motion Prediction) and D (Subsurface Imaging). Hole, J. A. (1992). Nonlinear high-resolution three-dimensional seismic travel time tomography, J. Geophys. Res. 97, 6553-6562.
Intern(s): Tracy Pattelena

Kim Olsen, University of California, Santa Barbara
David Okaya, University of Southern California

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Project Description: Project rank: 1. Use of the HAZUS program developed by the Federal Emergency Management Agency to assess earthquake losses in Los Angeles. I would like to work on this type of project because I have an interest in urban geography and the effects of natural hazards on large urban areas. 2. SCEC INSTANeT News Webservice (Interviews of SCEC Scientists, Writing and Editing of Articles, creating web pages, e-mailing updates). outmean: SCEC's Outreach program is designed to communicate to the general public the practical benefits of earthquake related research and its positive effects on the community. Public education about earthquake phenomena is very important to the people of Los Angeles, and this program informs them about the local hazards. projectgoals: I am unfamililar with the HAZUS program; however, my father has told me that SCEC is interested in HAZUS applications. From what I have heard the project sounds intriguing. I am taking a geography course this semester, "LA and the American Dream", that deals with many related topics. I hope to expand my knowledge with more hands-on experience. project importance: Being able to estimate and reduce earthquake losses has become extremely important for urban planning. Each of these projects takes us one step closer to this goal. personalgoals: I have not had previous experience with an internship. However, my father, Thomas Jordan, is a scientist at USC and his work over the years has spawned my interest in Earth Sciences and related fields. Though my experience is little, I am willing to learn. Right now my declared major is Environmaental Studies. I have not decided whether I will pursue this major, but I plan to work in a science-related field. I am applying for this internship in order to gain experience and explore subjects that may interest me in the future.
Intern(s): Alexandra Jordan

Mark Benthien, University of Southern California

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Nonlinear Network Dynamics on Earthquake Fault Systems

Project Description: Earthquake faults occur in interacting networks having emergent spacetime modes of behavior not displayed by isolated faults. Using simulations of the major faults in southern California, we find that the physics depends on the elastic interactions among the faults defined by network topology, as well as on the non-linear physics of stress dissipation arising from friction on the faults. Our results have broad applications to other leaky threshold systems such as integrate-and-fire neural networks.
Intern(s): Paul Rundle

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Seismic Hazard Assessment of the San Joaquin Hills using GIS

Project Description: The earthquake potential and risk of seismic events in the San Joaquin Hills region of Orange County must be assessed. This area has recently been recognized as having the potential to generate a significant earthquake. These hazards should be immediately analyzed and assessed so that hazard mitigation may be incorporated into the region's rapid development. Hypothesis- The San Joaquin Hills region is an area of active faults whose history of seismicity should be incorporated into regional development. By studying the earthquake potential of Quaternary-age faults in the region, the seismic hazard can be evaluated. Materials/supplies needed- Time in an ARCView GIS lab and miscellaneous supplies (provided at University of California, Irvine).
Intern(s): Daniel Raymond

Lisa Grant Ludwig, University of California, Irvine

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Data collection and analysis of Hector Mine Post-seismic GPS data

Project Description: After the October 16, 1999 M7.1 Hector Mine earthquake, there has been a focused effort on collecting postseismic deformation data. Within 48 hours of the quake, GPS receivers were set up around the fault. Since then, continuous GPS sites have been installed and repeated campaign GPS measurements have been made in the area surrounding the fault rupture. By measuring the postseismic deformation, we hope to capture the short-term after-slip and relaxation of the crust. Studying these phenomena will give us a better understanding of fault mechanics, the earthquake cycle, and the rheology of the crust. The project will involve data collection, data analysis and modeling. In June, we spend several days collecting campaign GPS measurements at sites on the marine base that are part of the SCEC Hector MIne postseismic network. The data collection will be done with Ashtech Z-12 GPS receivers, which will be set-up on each site for at least 24 hours. These observations will extend the time series for the postseismic network stations, last surveyed in April, 2000. The measurements, and data from continuous sites, will be analyzed using GIPSY-OASIS II software. The project plan is to complete the data analysis for all existing Hector Mine GPS data through mid-July, 2000. This work will include integrating campaign and continuous measurements mad since mid-March with the earlier data. Once the data have been collected and analyzed, we will model the results using simple dislocations in an elastic material. This type of modeling will allow us to see if there was any afterslip on or surrounding the coseismicinvert for the fault slip distribution that best fits the postseismic time series. We will also be able to determine if the data cannot be fit by afterslip alone, and requires models that include crustal relaxation.
Intern(s): Teresa Baker

Susan Owen, University of Southern California

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