Project Title: Modeling Crustal Deformation and Seismic Hazard in Southern California Using Geodesy, Geology, and Seismology: Preparing for the Plate Boundary Observatory
Mendenhall Fellow: Gregory J. (Greg) Anderson, (626) 583-6799, ganderson@usgs.gov
Duty Station: Menlo Park
Start Date: December 16, 2001
Education: Ph.D., 1999, Earth Sciences, University of California, San Diego
Research Advisors: Kenneth Hudnut, (626) 583-7232, hudnut@usgs.gov; William Prescott, (650) 329-4860, wprescott@usgs.gov; Malcolm Johnston, (650) 329-4812, mal@usgs.gov
Project Description: Southern California is home to almost 20 million people and has 50 percent of the $4.4 billion annualized earthquake risk in the United States. It is thus vital to better understand and quantify the earthquake process in this region. A key part of this is understanding the regional tectonic framework through geodetic crustal deformation studies. New datasets being developed through the work of scientists at the Southern California Earthquake Center (SCEC) and the U.S. Geological Survey (USGS) show the deformation field and known fault structures of southern California in unprecedented detail. Greg is using these data to model the present-day tectonics of southern California and to examine possible sources of time-dependent deformation such as lower crustal relaxation following recent large earthquakes. He is also using these data to estimate earthquake probability in southern California for comparison with estimates being developed by other workers and for inclusion in future seismic hazard estimates. More generally, although the current work is applied to southern California, the analysis and modeling methods being developed can be applied anywhere with a good long-term geodetic data set. In the future, this may include the proposed Plate Boundary Observatory, which, if completed, will cover the entire Pacific-North American plate boundary with a network of geodetic stations.For the past several years, scientists from SCEC and the USGS have been developing a synthesis of crustal deformation data across southern California including trilateration, very long baseline interferometry, satellite laser ranging, long-baseline and borehole strainmeters, and Global Positioning System (GPS) observations from both field surveys and the dense, continuously-operating Southern California Integrated GPS Network (SCIGN). The most recent version of this work consists of crustal deformation velocity measurements at about 650 sites, including the effects of large earthquakes, and will shortly be released as Version 3 of the SCEC Crustal Motion Map (CMM); this will be the best representation of regional crustal deformation anywhere in the world. At the same time, SCEC and USGS scientists are creating a database of information on known active faults in the region, as part of the Regional Earthquake Likelihood Models (RELM) project. The database will contain 3-D location and orientation as well as slip and slip-sense data, the known history of large events from palaeoseismology, and whatever other information is available for a given fault. When complete, it will represent the geological community's best understanding of faults in this area.
Greg is using these data to better understand the tectonics and earthquake hazard of southern California. His project has four main goals: (1) to estimate the present-day secular (steady-state) crustal deformation field across southern California; (2) to uncover and model sources of possible time-dependent deformation in this region; (3) to estimate earthquake probability using the same and other appropriate supporting data; and (4) to develop methods for modeling crustal deformation and estimating seismic hazard that can be used in later experiments.
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