HR: 0800h
AN: S41A-0952    [Abstracts]
TI: Earthquake Dynamics at Linked Fault Stepovers
AU: * Oglesby, D D
EM: david.oglesby@ucr.edu
AF: Department of Earth Sciences, University of California, Riverside, Riverside, CA 92521 United States
AB: Previous studies of strike-slip fault systems with linking dip-slip faults (Oglesby, 2003) have indicated that with equivalent shear and normal stresses on all segments, extensional stepovers with linking normal faults are more likely to produce multi-segment events that rupture the entire fault system, compared to compressive stepovers with linking thrust faults. This difference is due to the sign of the normal stress increment that the strike-slip faults radiate onto the linking dip-slip fault: in the extensional stepover, this stress increment is also extensional, unlocking the linking fault, and aiding rupture. In the compressional stepover, the normal stress increment is compressional, tending to lock the linking fault. In the current study, we use simplified assumptions about the scaling of stress in the interseismic period to investigate the behavior of fault stepover systems with more realistic pre-stress patterns. We assume that the linking fault is a passive feature that is loaded by sequential slip of the neighboring strike-slip faults. We find that such an assumption tends to accentuate the difference between the extensional and compressional fault systems. Under simple initial conditions and assumptions, extensional stepovers produce a larger number of events that rupture through the linking fault and rupture the whole system. Compressional stepovers have a tendency to lock up both during rupture and during the interseismic period, decreasing their ability to produce multi-segment events. The results may have implications for seismic hazard near these fault systems.
DE: 7260 Theory and modeling
DE: 7209 Earthquake dynamics and mechanics
DE: 3230 Numerical solutions
SC: Seismology [S]
MN: 2004 AGU Fall Meeting