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Plate Boundary Deformation Project


This is a joint project of the BSL, CIW, USGS, and UCSD to develop an integrated pilot system of instrumentation built upon existing infrastructure to study plate boundary deformation in central California, with special emphasis on its relation to earthquakes (Figure 7.1).

Because the time scales for plate boundary deformation range over at least 8 orders of magnitude, from seconds to decades, no single technique is adequate. We have proposed an integrated approach to provide a broadband characterization of surface deformation that makes use of three complementary and mature geodetic technologies: continuous GPS, interferometric synthetic aperture radar (InSAR), and borehole tensor strainmeters. In addition, ultrasensitive borehole seismometers will monitor high-frequency seismic deformation due to microearthquake activity.

The project has three components. One will enhance existing instrumentation along the Hayward and San Andreas faults in the San Francisco Bay Area. We will acquire and install 10 new borehole strainmeters (complementing 6 existing ones), and 7 new continuous GPS stations (complementing 18 existing BARD stations in the Bay Area). Although funding has not been secured yet, we also plan to acquire and install 10 borehole seismometer systems (complementing those in the Hayward Fault Network), jointly with the strainmeters. The data will be continuously telemetered over frame relay to U.C. Berkeley and made available to the community through the Northern California Earthquake Data Center (NCEDC).

The second component of this project is to enhance the monitoring of the Parkfield segment of the San Andreas fault by acquiring and deploying 8 continuous GPS stations. The third component is in support of a 5-m X-band SAR downlink facility in San Diego to collect and archive radar imagery to obtain InSAR data that will be available for integration with the continuous GPS, strainmeter and seismometer data. The data will be made available through the NCEDC and SCEC data centers.

Siting and Hardware Issues

This year, the BSL has focused primarily on site selection for the integrated network in the Bay Area, in cooperation with the USGS. Figure 7.1 shows the planned configuration. Sites currently being pursued are MHDL (Marin Headlands) and HAMF (Hamilton Field) in the North Bay, PTWN (Pt. Wilson), PTPB (Pt. San Pablo), and STMC (St. Marys College) in the East Bay, MONT (Montara) on the Peninsula, and YERB (Yerba Buena Island) in the Bay. Site evaluation of geologic properties, sky visibility, ease of permitting, and power and telemetry, were performed at most of the sites, and permitting has been secured at several (PTWN, HAMF, MHDL, and MONT). We are continuing evaluations and permitting at SMTC, YERB, and PTPB, where sites suitable for both GPS and strainmeters have proven more difficult to locate.

After review, it was decided to purchase Quanterra 330 datalogger systems for the project. These have been ordered and delivery is scheduled for December, 2000. Additional site issues, such as serial data configuration and telemetry are under review. The strainmeters are currently under construction at CIW and should be ready for emplacement in 4-6 sites when drilling is scheduled to begin in Spring 2001.


This project is sponsored by the National Science Foundation under the Major Research Instrumentation (MRI) program with matching funds from the participating institutions and the Southern California Earthquake Center (SCEC).

Barbara Romanowicz, Roland Bürgmann, Mark Murray, Paul Silver (CIW), Alan Linde (CIW), Malcolm Johnston (USGS), Wayne Thatcher (USGS), Yehuda Bock (UCSD), and Dave Sandwell (UCSD) are the principal investigators on this project.

Mark Murray, Ray Baxter, and Rich Clymer have been involved in site selection for the BSL. Mark Murray and Lind Gee contributed to the preparation of this chapter.

Figure 7.1: GPS (triangles) and borehole strainmeters (circles) in northern California (top) and the San Francisco Bay Area (bottom). Existing stations are shown in open symbols. Proposed components of the plate boundary deformation project, shown in shaded symbols, include 8 GPS in the Parkfield region along the central San Andreas fault, and 10 borehole strainmeters and 7 GPS receivers in the Bay Area. Existing GPS receivers will occupy the remaining 3 strainmeter sites.
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