Overview

The U.S. Geological Survey is coordinating an ambitious undertaking, which involves scientists at many institutions, to re-examine the source characteristics of the 1906 earthquake, to use a broad range of data to improve our understanding of the three-dimensional structure of the Earth's crust in northern California, and to use this information to simulate strong ground motion from the 1906 Mw 7.8 San Francisco earthquake. One goal of these simulations is to reproduce as accurately as possible the ground motion that actually occurred in 1906. Because the 1906 earthquake occurred before instruments could accurately record strong ground shaking, we compare the simulated shaking with the best data available. These are intensity observations, which characterize the strength of shaking as it affects buildings and as it is perceived by eyewitnesses. This comparison allows us to assess the validity of the simulations. The next large earthquake on the northern San Andreas fault is likely to differ in important ways from the 1906 event, so in addition to simulating a repeat of the 1906 rupture, we have considered alternative scenario earthquakes that have different epicenters, distributions of slip, rupture speeds, and rupture directions. The results of these simulations will be used by earthquake engineers to assess the likely impacts of future earthquakes along the San Andreas fault.

Timeline

Event	Target	Actual
Project start		Jun 6, 2004
Velocity model delivered	May 18, 2005	Jul 22, 2005
Source model delivered	Oct 31, 2005	Jan 12, 2006
Loma Prieta ground motions delivered	Jan 18, 2006	Jan 17, 2006
First 1906 ground motions delivered	Feb 15, 2006	Feb 24, 2006
Final 1906 ground motions delivered	Mar 1, 2006	Mar 8, 2006
SSA/EERI Meeting		April 18-21, 2006