固体地球物理学术报告通知-David Oglesby

We use 3D dynamic finite element models to investigate potential rupture paths of earthquakes propagating along faults through the western San Gorgonio Pass (SGP), a structurally complex region along the San Andreas fault system (SAF) in southern California.  We focus on the San Bernardino strand of the SAF, the San Gorgonio Pass Fault Zone, and a portion of the Garnet Hill strand of the SAF.  The San Bernardino and Garnet Hill strands are predominately right-lateral strike-slip faults, while oblique thrust faults dominate the San Gorgonio Pass Fault Zone.  We use the finite element method code FaultMod (Barall, 2009) to observe differences in rupture propagation along a fault geometry that reflects current understanding of the 3D complexity, and is consistent with long-term loading and observed surface deformation.  We test three different types of pre-stress assumptions: 1) constant tractions (assuming pure right-lateral strike-slip motion on the San Bernardino and Garnet Hill strands and oblique thrust/right-lateral strike-slip motion on the San Gorgonio Pass Fault Zone), 2) a uniform regional stress regime, and 3) long-term (evolved) stress from quasi-static crustal deformation modeling. Our results imply that under the more realistic regional stress and evolved stress assumptions, through-going rupture propagation from the southeast to northwest (i.e., from the Garnet Hill to the San Bernardino strand) may be more likely than through-going rupture in the reverse direction (from the San Bernardino strand to the Garnet Hill). The results may have implications for the earthquake potential in the region, as well as for ground motion in the Los Angeles Basin. The results also emphasize how fault geometry and stress patterns combine to influence rupture propagation on complex fault systems.