IGPP Seminar Series

Present-day Stress Along the San Andreas Fault System

by Prof. David Sandwell
Scripps Inst. Oceanography/UCSD IGPP


The earthquake cycle is much longer than the span of seismic and geodetic measurements so computer models will be needed to forecast major ruptures. We have developed a 3D semi-analytic, time-dependent earthquake cycle model that is used to simulated deformation and stress accumulation along the San Andreas Fault System over the past 1000 years. Present-day stress accumulation rate is well resolved by the growing network of GPS measurements. Present-day slip rate is consistent with geologic estimates as long as the fault locking depth is allowed to vary along the fault system. We find an inverse correlation between average earthquake recurrence interval and Coulomb stress accumulation rate that is consistent with earthquake stress drops of 1-6 MPa. The present-day level of stress on the San Andreas Fault shows high Coulomb stress on the Coachella segment in accordance with the lack of a historical earthquake on this segment. The largest uncertainty in present-day stress is due to our incomplete knowledge of slip during historic and paleoseismic ruptures.
Tuesday, 24 October 2006
3845 Slichter Hall
Refreshments at 3:45 PM
Lecture at 4:00 PM