Active faulting near the Cajon Pass well, southern California; Implications for the stress orientation near the San Andreas Fault

Abstract

The DOSECC Cajon Pass well is located 4 km NE of the San Andreas fault in a region that includes a diversity of secondary structures. Active faults close to the well are subparallel to the right‐lateral San Andreas fault but exhibit left‐lateral and normal slip. The stress orientation measured in the well is not consistent with right‐lateral slip on the San Andreas fault or the stresses inferred from focal mechanisms of earthquakes within 10 km of the fault, but may drive the E‐striking, slightly normal, left‐lateral Cleghorn fault, the closest active fault to the well. If the in‐situ stress is everywhere consistent with the highly variable styles of active secondary faulting like the Cleghorn, the orientation of stresses along the San Andreas fault may be quite variable.