Source characteristics of large strike-slip earthquakes

We investigate complex earthquake source processes using both spontaneous dynamic rupture modeling and kinematic finite-source inversion. Dynamic rupture modeling is an efficient tool with which we can examine how stress conditions and frictional behavior on a fault plane play a role in determining kinematic motions on the fault and the resulting ground motions at the Earth's surface. It enables us to develop a physical understanding of the earthquake rupture process in terms of Newtonian mechanics. We construct a set of spontaneous dynamic rupture models for several recent earthquakes in Japan and California in order to have a physical understanding of the earthquake source processes for several specific events. Our dynamic models are used to investigate the scaling properties of dynamic source parameters, i.e., fracture energy and stress drop. Many interesting features of the earthquake source process can also be inferred from the kinematic source inversion of observed seismic or geodetic data. We carry out a comprehensive source study of the 1906 San Francisco earthquake by re-analyzing both geodetic and seismic data in order to reconcile two existing, and mutually inconsistent, source models and obtain a unified one. Our study has important implications for seismic hazard in California, and perhaps more generally for large strike-slip earthquakes. Lastly it is important to utilize our knowledge of the earthquake source to improve our understanding of near-field ground motion characteristics because source complexities are quite uncertain and can be the dominant factor in determining the characteristics of near-field ground motion. We develop a pseudo-dynamic source modeling method with which we can generate physically self-consistent finite source models of large strike-slip earthquakes without high-cost, fully dynamic rupture simulation. The new pseudo-dynamic modeling method enables us to effectively characterize the earthquake source complexities for realistic ground motion simulation, especially for large strike-slip events.