Using GPS Displacement Vectors to Estimate Slip Rates of the San Andreas Fault System within the Indio Transect

RM 211

To better predict the potential magnitude of an earthquake and thus prepare appropriate precautions for associated hazards, it is essential to understand what a fault is doing from every facet. Elastic rebound theory aids in this understanding. The theory entails that as shear stress is applied along a fault and strain accumulates in the upper crust due to bending of the tectonic plates, so does elastic energy; when friction is exceeded, slip on the fault occurs, releasing the elastic energy that had been stored. The purpose of this study was to relate the rate of elastic bending of tectonic plates at surface to the true slip rate at depth. Modeling methods using an equation from elastic theory were used to compare the velocity profile predicted for various slip rates with measured GPS velocities. This project examines transect across the Pacific-North American plate boundary bisecting a portion of the San Andres Fault (SAF) system near Indio, California. This transect spans four major faults, which are the Rose Canyon fault (RCF), Julian section of the Elsinore Fault(EFJS), Anza section of the San Jacinto Fault Zone(SJFA), and Coachella section of the San Andreas Fault Zone (SJFC). The locking depths for each fault were estimated from the maximum depth of seismicity. The preferred model produced slip-rates yielding 4 mm/yr. for the RCF, 1 mm/yr. for EFJS, 19 mm/yr. on SJFA, and 21 mm/yr. on the SAFC.