The amount and distribution of seismic slip along 240 km of the San Jacinto fault zone between Cajon Pass and Superstition Mountain has been obtained from determinations of seismic moment and estimates of source dimension for each of the nine moderate earthquakes (6 < M < 7) which have occurred there since 1890.
There are two significant gaps in seismic slip, one between Cajon Pass and Riverside, the other from Anza to Coyote Mountain. Each is about 40 km long and both are characterized by complex fault zones and a currently high level of minor seismicity (M < 5). No aseismic fault creep has been identified on either segment. These gaps may mark the sites of the next moderate earthquakes (M = 6 → 7) to occur along the San Jacinto fault zone. The two remaining sections of the fault, Riverside and Anza, and Coyote Mountain to Superstition Mountain, may have been ruptured along their entire lengths, in 1890–1923 and 1942–1968, respectively.