Late Quaternary slip rate of the western Pinto Mountain Fault, Morongo Valley, CA

Through San Gorgonio Pass, the San Andreas Fault system forms a restraining bend, locking the fault and creating an apparent slip and earthquake deficit in this region (e.g., Matti and Morton, 1993; Yule and Sieh, 2003; Cooke and Dair, 2011). The potential for a major through-going rupture on this portion of the fault hinges upon our understanding of potential pathways for earthquakes. A ?southern? pathway along the Banning, Garnet Hill, and San Gorgonio Pass strands of the San Andreas Fault (Figure 1) accounts for only a fraction of the slip and large earthquakes when compared to strands to the northwest and southeast of the pass (Yule et al., 2014; Heermance and Yule, in preparation). A hypothesized ?northern? pathway along the Mission Creek and Mill Creek strands (Figure 1) can potentially increase the slip rate and earthquake recurrence in the San Gorgonio Pass region to bring them more in line with rates and recurrence outside of the pass (e.g., Oskin et al., 2015). However, this hypothesis is at odds with work that suggests the Mission and Mill Creek strands have been abandoned, or nearly so, following a reorganization of the San Andreas Fault system ~150,000 yrs ago (Matti et al., 1992; Matti and Morton, 1993; and Kendrick et al., 2015).