Study of Earthquake Triggering in a Heterogeneous Crust Using a New Finite Element Model

Abstract

Research on earthquake triggering and stress transfer is important for understanding earthquake occurrence. Based on the work of Chinnery (1963), Rybicki (1973), Yamashina (1978), and Das and Scholz (1981), numerous studies have been made in this direction after Stein and Lisowski (1983) introduced the concept of Coulomb failure stress change, Δ CFS ( e.g. , Oppenheimer et al. 1988; Reasenberg and Simpson 1992; King et al. 1994; Harris et al. 1995; Parsons et al. 2008; Toda et al. 2008). All the existing work has been based on the dislocation theory in a uniform isotropic elastic half-space ( e.g. , Okada 1992). Active plate boundaries are often composed of highly heterogeneous crust ( e.g. , McNamara and Walter 2001). In the interior of a plate, the crust may also be heterogeneous ( e.g. , McNamara and Walter 2001). For example, the lateral velocity variation in the crustal velocity of P waves in South Australia ranges from 5.9 to 6.5 km s–1 (Clifford et al. 2007). All these crustal heterogeneities will affect the redistribution of stresses after a large earthquake. Zhao et al. (2004) showed that high aftershock activity following the 2000 Tottori earthquake ( M 7.3) in Japan was associated with areas of high P -wave velocity. Progress in the study of the effect of crustal heterogeneity on earthquake triggering and stress transfer has been slow, partly because the dislocation theory cannot include crustal heterogeneity in its calculation. Wang et al. (1980, 1983) first investigated earthquake risk and stress transfer among the multiple faults in North China. Wang and Cai (1997) investigated the response of the complex fault system in the San Francisco Bay area to small changes in the regional stresses. Freed and Lin (1998) studied the stress transfer in a vertically layered crust. These studies, however, …