1 Appendix F Estimated Changes in State on San Francisco Bay Region

In the 70 years prior to the great 1906 San Francisco earthquake, seventeen M≥6 earthquakes shook the San Francisco Bay region; in the 94 years following there have been only five (Bakun, 1999). A plausible explanation is that after great earthquakes the crust in an entire region is relaxed, creating a "stress shadow" within which other large earthquakes are suppressed until plate tectonic stresses gradually reload the faults (Ellsworth and others, 1981; Harris and Simpson, 1998). Calculations indicate that every major fault system in the Bay region was relaxed to some degree by the 1906 event (Figure 1).