State of stress in seismic gaps along the San Jacinto Fault

Abstract

Data from the Southern California Seismic Network have been extensively used to map spatial and temporal variations of seismicity (for example, Hileman et al., 1973; Green, 1983; Webb and Kanamori, 1985; Doser and Kanamori 1986; Nicholson et al., 1986). A recent study by Sanders et al. (1986) clarified some of the important features of historical seismicity along the San Jacinto fault of southern California, one of the most prominent being the Anza seismic gap. Thatcher et al. (1975) investigated the spatial distribution of large earthquakes along the fault and indicated that a 40-km-long section from Anza to Coyote Mountain is deficient in seismic slip and can be considered a seismic gap (G1 in fig. 1). Sanders and Kanamori (1984) investigated the seismicity along an 18-km-long section (also often called the Anza seismic gap) centered near the town of Anza, and concluded that this section of the fault is locked and has the potential for a magnitude 6.5 event (G2 in fig. 1). In this paper, we review the most recent activity along the San Jacinto fault and assess the seismic potential of this fault zone in light of an empirical relation between fault length, seismic moment, and repeat time obtained from earthquakes along active fault zones around the world.