Numerical Models of Post-Seismic Deformation Following the 1906 San Francisco Earthquake

The M 7.8 1906 Great San Francisco earthquake ruptured 470 km, or about a third of the San Andreas fault, producing offsets of up to 8.5 m. We are studying the long-term effects in the strain field generated by this earthquake and comparing model results using the 3D GeoFEST code combined with the DISLOC elastic dislocation code with observed data. We are comparing model results with current GPS data in order to quantify the contribution of post seismic deformation from large earthquakes to the current velocity field. Viscoelastic models indicate 2-6 mm/yr of post-seismic deformation resulting from postseismic relaxation following the 1906 event. Our model results best fit the GPS data from Bay Area Regional Deformation (BARD) network using a 40 yr relaxation time and an 18-30 km locking depth for the San Andreas, Hayward, and Calaveras faults.