San Francisco Bay Area Earthquake Simulations: A Step Toward a Standard Physical Earthquake Model

Abstract

SUMMARY: Earthquakes in California’s San Francisco Bay Area are likely to be more strongly affected by stress inter-action than earthquakes in any other place in the world because of the region’s closely spaced, sub-parallel distribution of faults. I believe therefore, that meaningful quantification of earthquake probability and hazard in the Bay Area can be made only with the guidance provided by physically-based and region-wide earthquake models that account for this interaction. This paper represents a first step in developing a Standard Physical Earthquake Model for the San Francisco Bay Area through realistic, 3000-year simulations of earthquakes on all of the area’s major faults. These simulations demonstrate that a Standard Physical Earthquake Model is entirely feasible, they illustrate its application, and they blueprint its con-struction. A Standard Physical Earthquake Model provides the mechanism to integrate fully the diverse disciplines within the earthquake research community. As a platform for data utilization and verification, a physical earthquake model can employ directly any earthquake property that is measurable in the field or in the laboratory to tune and test its seismicity products. As a platform for probability forecasts, a physical earthquake model can supply rational estimates of every imaginable earthquake statistic while simultaneously satisfying all slip and earthquake rate constraints. As a platform for hazard analysis, a physical earthquake model can compute earthquake shaking intensity from first principles by convolving a full suite of rupture scenarios with site-specific dislocation Green’s functions. Physical earthquake models have advanced greatly in the last decade. Simulations of earthquake generation and recurrence are now sufficiently credible that such calcu-