2004 Research Projects

GPS Monitoring of the San Andreas and San Jacinto Faults

Project Description: We present the results of 5 GPS campaigns conducted by Cal State San Bernardino and Harvey Mudd College. Data were collected from twelve different sites along a swath stretching from Norco through San Bernardino to Lucerne Valley, crossing the San Jacinto, San Andreas and Helendale faults. The data were processed using JPL's Auto GIPSY software in point-positioning mode. We have successfully processed about 70% of the Rinex files. All of the stations show northwestward movement relative to the site PIE1 on the North American plate with velocities ranging from 4.1 +/- ** mm/yr for LUCS in Lucerne Valley to 37.7 +/- ** mm/yr for CLSA in Riverside. The station with the most tightly constrained velocity estimate is SANO (33.7 +/- ** mm/yr), in western Riverside. This is also the station for which we have the longest record; we have processed SANO data from as early as 1995 that is available at the SCEC data center website. We expect that the velocity estimates for the other stations will become more tightly constrained as we (1) continue to collect data during future campaigns, (2) discover the reasons why were unable to process 30% of our data, and (3) take advantage of the bias-fixing option in AutoGIPSY processing. For instance, while the uncertainty in the resultant veloctiy for CLSA is 15.68 mm/yr, the uncertainty for SANO is only 1.7mm/yr. One of our ultimate goals is to use these data to help determine the locking depths and slip rates of the San Andreas and San Jacinto faults in the San Bernardino area. At this point the uncertainties in our geodetic velocity estimates are too large to distinguish between competing models regarding the relative importance of the San Andreas and San Jacinto faults in the plate boundary system. Another goal of the CSUSB/Harvey Mudd GPS campaigns is to introduce undgraduate students and high school science teachers to Earth Science research. Our summer campaigns have an educational component, including two days of pre-campaign training on the scientific goals of the project and proper set-up procedures for accurate data collection as well as a two-day post-campaign workshop on interpreting and modeling GPS data. A total of 80 people have participated in the 5 campaigns conducted to date, including 23 college students from under-represented ethnic groups and 23 teachers.
Intern(s): Nicholas Vaughn

Sally McGill, California State University, San Bernardino

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Paleoseismic studies on the Chino fault

Project Description: We initiated a 3-D paleoseismic investigation approximately 4 km northwest of Prado Dam to quantify the slip rate of the southern portion of the Chino fault. The trench site is located at the mouth of a small deflected canyon at the front of the Chino Hills where the Chino fault juxtaposes degraded old alluvial fan surfaces to the northeast from bedrock of the hills to the southwest. Near the trench site the fault was mapped by an alignment of benches, tonal lineaments, saddles and right-laterally offset drainages. Our excavations revealed a 40- m- wide zone of apparently inactive northwest-striking high angle faults that coincides with the geomorphic expression of the Chino fault. These faults cut bedrock of the Miocene age Puente Formation but do not deform overlying colluvium, channel and debris flow deposits. Based on the degree of soil development in deposits overlying the fault zone, we infer that the bedrock faults have not ruptured since at least the late Pleistocene. The geometry of a bedrock channel margin exposed in one of the trenches further suggests that the fault has not experienced recent right lateral movement. Radiocarbon dates from deposits overlying the fault zone are pending. Trenches upslope and to the west of the mapped main trace of the Chino fault revealed a 10- m- wide low-angle reverse fault zone that dips 10 to 30 degrees to the southwest and juxtaposes bedrock over older alluvial fan deposits. This is similar to the expression of the fault in geotechnical trenches to the north and south of our site. By contrast, the only known active strands of the fault are nearly vertical. To date we have found no indications of Holocene activity on the Chino fault at our trench site. Work to determine the timing of past earthquakes on the low angle faults at our site is ongoing, but the site is probably not going to assist us in determining a lateral slip rate.
Intern(s): Melissa Tanney

Chris Madden Madugo, Earth Consultants International
Eldon Gath, Earth Consultants International

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Using local seismic events to map the San Gabriel Mountains Bright Spot

Project Description: Data returned from the LARSE I experiment in 1994, which consisted of information gathered from a series of man-made seismic events, showed a zone of high velocity beneath the San Gabriel Mountains. This zone was named the San Gabriel mountains Bright Spot (SGMBS). In order to try and further characterize this zone, I spent the summer working on a project at the University of California, Los Angeles, working under Dr. Paul Davis. The aim of this project was to try and find reflection phases from the SGMBS in local seismic events. We looked primarily for P-P and P-S phases, which is what showed up in the LARSE I survey, as well as spending some time looking for S-S and S-P phases. While nothing conclusive was determined, lining up seismograms at the expected arrival times for the reflection phases yielded some promising results.
Intern(s): Dave Schumaker

Paul Davis, University of California, Los Angeles

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(no name)

Project Description:
Intern(s): Yekaterina Prudchenko

Greg Beroza, Stanford University


Deployment to Investigate Long Period Earthquakes and Remotely Triggered Earthquakes at The Geysers Geothermal Reservoir

Project Description: The Geysers in Northern California is one of the most seismically active geothermal sites in the world, having at least one hundred earhquakes of magnitude greater than 1.4 per day [Ross et al., 1999]. Previous studies conducted suggests that there has been remote triggering within The Geysers, with at least 11 examples noted so far [Stark and Davis, 1996; Gomberg and Davis, 1996; Prejean et al., 2004]. Remote triggering is when regional events (> 100km distance) trigger a swarm of seismicity. There is some evidence that remote triggering is more common at geothermal sites, such as The Geysers. This year marks the first time that broadband seismometers were utilized in The Geysers. The four Guralp 6-TD broadband seismometers deployed in The Geysers are able to measure both the seismic waves of regional events and local earthquakes at the same time. The installation of the broadband seismometers can assist in the study of the relationship between regional events and its resulting seismic triggering. The goal of this project is to set up a Antelope database for the data collected and see if there is clear evidence of remote triggering. As well, geothermal areas like The Geysers often have long-period seismicity and we will investigate to see if this is evident in The Geysers reservoir.
Intern(s): Oliver Yan

Emily Brodsky, University of California, Santa Cruz

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Developing an integrated rock mechanics-seismological database, field guide, and model for exhumed seismogenic faults in southern California.

Project Description: The need for a guidebook of active and inactive faults in southern California has been growing in recent years. This poster is an overview of the guidebook. The guidebook will provide information about several important exhumed faults in southern California that have been important sites for modern undrstanding of fault composition and structure. Information at each fault location will include: location of site and clear directions, basic geological and seismological information, rock type, exhumation amount, fault history, understanding of fault geometry, segmentation, and references to appropriate papers. When applicable: physical characteristics, geometry of fault zone, chemical characterization, and particle size distribution will be included. Fault exposures provided in the field guide are: four locations along the San Andreas fault, three locations along the Punchbowl fault, four locations along the North Branch San Gabriel fault, and two locations along the San Gabriel fault. This list is not complete, and suggestions for data and locations are welcome.
Intern(s): David Forand

James Evans, Utah State University

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Visualization and Graphical User Interface for a new, experimental Mimetic Code for Pathway 3 in the SCEC ITR collaboration

Project Description: My summer work as a SURE intern was focused on Geoff Ely’s new Support Operator Rupture Dynamics code (SORD), designed to model earthquake rupture in nonplanar geometries. SORD was developed and is being tested and validated in rapid-prototype form using MATLAB. It will ultimately be ported to a very large scale multi-processor environment at the San Diego SuperComputer Center (SDSC). SORD implements a so-called “mimetic” finite-difference discretization of the equations of motion of continuum mechanics, on a noncartesian, yet logically rectangular, three-dimensional mesh. This allows modeling of surface topography as well as rupture on nonplanar faults, capabilities that have previously been the exclusive domain of finite element models using unstructured meshes. My projects dealt with the development and testing of visualizations of the code output in MATLAB. I experimented with small-scale runs using different visualization parameters in order to highlight various aspects of the output wave fields. I also ran larger scale models to help test the code, to verify that the visualization was displaying correctly in the limit of high resolution, and to ferret out possible anomalies in the simulations. As well, I set up the SIO Geowall and used it to display the 3-D visual aspects of the code. A challenging coding aspect of my project was to create a graphical user interface (GUI) for SORD in order to facilitate the creation of animations (movies). I developed a GUI frame in which the user selects particular runtime parameters or a “run style” of pre-selected parameters. I used the code to capture animations of the ground motions associated with spontaneous earthquake rupture, and adapted the GUI to display and control the resulting movies. I also experimented in a very preliminary way with exporting visualization clips to other movie-development environments. My poster will show examples of various visualization, as well as interactive demonstrations of the GUI and the movie capture capability, including several different views of SORD output. This will include a view in spherical coordinates, a depth plane view, and a stereo view of spherical coordinates, which can be viewed in stereo. At Yale, I am a senior studying applied math with concentrations in physics and geology/geophysics. Overall, I thoroughly enjoyed my summer experience at IGPP and with SCEC. My knowledge of earthquakes greatly increased, as well as my programming skills. The SCEC SURE Summer Internship was extremely fun and educational.
Intern(s): Annemarie Baltay

Bernard Minster, University of California, San Diego

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Processing of San Simeon Aftershock Data from SCEC, CSUN, and USGS Portable Seismic Stations

Project Description: Immediately following the M6.5 San Simeon earthquake, researchers from the Institute for Crustal Studies (ICS) and the SCEC portable broadband instrument center (PBIC) mobilized instrumentation to record aftershock activity associated with this event. Within the first 24 hours, three stations were deployed in the Paso Robles area, along with one station in Cambria, and one station in Atascadero. Two additional stations were deployed in early January at strong motion stations in San Luis Obispo and Cambria that had recorded the mainshock. California State University, Northridge (CSUN) also deployed two stations. The SCEC PBIC stations alone have detected over 2,700 events associated with the Northern California Earthquake Data Center (NCEDC) catalog. In addition to the SCEC PBIC deployment, the US Geological Survey (USGS) deployed six stations closer to the center of aftershock activity. The SCEC PBIC stations were installed along the perimeter of the aftershock sequence in urban areas while the USGS stations were deployed atop the main sequence of aftershocks in more rural locations. The USGS data was transferred to UCSB and has now been integrated with the SCEC/CSUN data into a single data set. We are in the process of associating the combined data with the NCEDC catalog and expect the number of recorded earthquakes to increase. The two deployments complement each other well and together should provide a very useful data set for more accurately determining event hypocenters, crustal structure, and for examining earthquake source properties.
Intern(s): Jack Tung

Jamison Steidl, University of California, Santa Barbara

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Developing STP for Windows and XML

Project Description: The Seismogram Transfer Program(STP) was developed for seismologists and other users who who have need to obtain seismic data. However, since there was only a UNIX/Linux version and an an internet version of STP, it was necessary to develop a client version of STP for PC users. A console version for Windows was developed for users who are more comfortable and experienced with the UNIX/Linux version of STP. This version allows users to enter commands in the STP command console, similar to the way they would using the UNIX/Linux version. However, for users who are more comfortable using the web version of STP, a GUI version was created. Some users of STP might want to use data that they have received for other applications. To accommodate these users a command allowing users to receive Phase and Event information in XML format was created. The Swiss Seismological Service developed an XML schema for the Event command, and have documented it on a site called QuakeML. However, because of certain restrictions coded within their schema, it was necessary for the SCEDC to create and maintain their own schema and documentation.
Intern(s): Omar Salman

Rob Clayton, California Institute of Technology
Vikki Appel, United States Geological Survey

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The Study of Submerged Shorelines of the Southern California Borderland Areas Focusing on the Northern Channel Islands Platform and Pilgrim Banks.

Project Description: Submerged shorelines preserved around the Northern Channel Islands platform within the Southern California Continental Borderland provide a unique datum for determining vertical tectonic motion. Last Glacial Maximum (LGM) and younger paleoshorelines are well preserved due to low frequency erosional forces that occur in the region and as such act as excellent strain markers, recording deformation over the last 18,000 years (about the time of LGM). These shorelines were originally formed close to sea level, but through time they have been submerged and deformed due to sea-level change, local vertical tectonic movement, and faulting. The purpose of this project was and continues to be to map potential paleoshorelines around the Northern Channel Islands and Pilgrim Banks to the south, using the information gained to investigate the Transverse Range – Peninsular Range intersection. The interaction between these two major provinces has created a structurally and tectonically complex area, which we have only just begun to investigate and understand. As we study the paleoshorelines and their relevance to vertical strain rates, in addition to the distortion of them that has taken place due to the faulting in this area, we will be able to gain further insight into the nature of the associated faults. This information can then be used to further understand the tectonics processes operating in southern California and the earthquake hazards they pose to coastal communities and the larger metropolitan areas.
Intern(s): Melissa Meiner

Chris Goldfinger, Oregon State University

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A Paleoseismic History of the San Andreas Fault in Wrightwood, California: 1000 B.C. - 500 A.D.

Project Description: A record of large earthquakes throughout historic and prehistoric time is essential to our understanding and prediction of fault behavior. A major tool for forecasting future quakes is the identification of their past frequencies. As the historical record of the San Andreas only includes one or two major events, we must do paleoseismic investigations to form a more complete record. The paleoseismic site near Wrightwood, CA has 5000 years of evidence for seismic events along the southern San Andreas fault. The record is preserved in deformed late Holocene debris flows and peat layers. Previous trenches in the site have provided evidence for 14 large earthquakes over the past ~1500 years as well as for earthquakes older than 3000 years BP. We excavated six trenches to complete the record of earthquakes in the missing period, 1000BC to 500AD and found several distinctive structural features including fissures, low angle faults, and anticlines. Although these features provide evidence of tectonic deformation, they do not well demonstrate all seismic events for the period in question. Additional excavations may provide a more accurate record of the events during this time.
Intern(s): Nissa Morton

Sally McGill, California State University, San Bernardino
Ray Weldon, University of Oregon

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Earthquake Information Made Accessible to Non-English Speakers

Project Description: Science has made many advances in the field of seismology, earthquakes in particular. We have learned to live with earthquakes, but most of the general public still does not understand the nature and mechanisms of earthquakes. For this reason, the Southern California Earthquake Center (SCEC) in partnership with the United States Geological Survey (USGS), the Federal Emergency Management Agency (FEMA) and the California Earthquake Authority (CEA) have developed an earthquake handbook for the general public. Although the information provided in this handbook is accessible to the public, it has only been published in English. The goal of SCEC's Communication, Education, and Outreach Program is to translate and publish the content of the handbook into Spanish, so that more of the population would benefit from the information. The content was translated into Spanish the summer of 2004, as close as possible to the English text. Images, figures, and tables were also translated. After the Spanish handbook has gone through the revision and suggestion phase, it will be published and distributed to the general public.
Intern(s): Monica Maynard

Mark Benthien, University of Southern California

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Surface deformation in the Western Salton Trough as observed by InSAR

Project Description: Data from 33 ERS-1 and ERS-2 interferograms (track 356, frame 2943) covering the Western Salton Trough and spanning a time period from 1992 to 2000 are analyzed in order to distinguish possible tectonic movement from subsidence due to groundwater withdrawal. Several areas of apparent deformation are observed: along the Superstition Hills/Elmore Ranch faults, near the southern end of the Coyote Creek segment of the San Jacinto fault, in the Borrego Valley, and near the northwest shore of Salton Sea. Faults in the area are known barriers to groundwater flow. Comparison with well draw-down data and surface geology suggests that the deformation signals in Coyote Creek, Borrego Valley, and Salton Sea area are primarily due to groundwater extraction. The deformation along the Superstition Hills/Elmore Ranch fault may be partially tectonic in origin as the amplitude of deformation matches closely with slip data 1987 Superstition Hill/Elmore Ranch earthquake.
Intern(s): Afton Van Zandt

Rob Mellors, San Diego State University

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