Collaborative Research: Modeling of 3-D Viscoelastic Stress Transfer in the California Crust: Implications for Earthquake Triggering and Seismic Hazard Migration

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Lin BurgmannThe investigators propose to perform a set of 3-D numerical modeling experiments, focusing on three recent California earthquake sequences: (1) the 1992 Landers earthquake, its potential role in triggering the 1999 Hector Mine event, and their combined effects on the southern San Andreas fault; (2) the 1983 Coalinga and 1985 Kettleman Hills blind-thrust quakes and their potential effects on delaying seismic rupture on the Parkfield segment of the San Andreas fault; and (3) the most recent sequence of historical quakes in the Los Angeles region, including the 1933 Long Beach, 1952 Kern County, 1971 San Fernando, 1987 Whittier Narrows, and 1994 Northridge events, and their implications on seismic hazard migration in the Los Angeles region. Recently the investigators have successfully developed preliminary 3-D viscoelastic models for a small subset of the above California sequences. This project will allow them to carry out a much more comprehensive investigation through (1) extending the models to include all relevant quakes, (2) verifying the robustness of the model solutions and their sensitivity to assumptions in crustal rheology and fault geometry, and (3) comparing the model results with geodetic observations. Results of this modeling investigation, together with advances in space geodesy and seismic monitoring capabilities, should provide us with a much clearer understanding of the seismic properties of the California crust, the mechanisms of earthquake triggering, and the regularities in seismic hazard migration in California. This is a collaborative project between the UC Berkeley (Andy Freed) and WHOI (Jian Lin). Freed will lead 3-D modeling experiments using the I-deas viscoelastic modeling code, while Lin will lead tasks of comparing the I-deas solutions to independent results from the GENPro boundary-element code and analyzing the geodetic and earthquake data in the study regions to constrain modeling.