HR: 13:55h
AN: S33C-02    [Abstracts]
TI: Multi-cycle Dynamics of Branched Fault Systems
AU: * Duan, B
EM: benchun@namazu.ucr.edu
AF: University of California,Riverside, 900 University Avenue, Riverside, CA 92521
AU: Oglesby, D D
EM: david.oglesby@ucr.edu
AF: University of California,Riverside, 900 University Avenue, Riverside, CA 92521
AB: Recent earthquakes such as the 1992 Landers, 1999 Hector Mine, and 2002 Denali fault (Alaska) have shown the importance of understanding the dynamics of branched fault systems. Realistic dynamic models of earthquakes on such systems require a fault stress field that is consistent with both tectonic loading and the fault event history. Toward this goal, we perform multi-cycle dynamic simulations on 2D branched fault systems by modeling both the dynamic rupture process and the interseismic loading process. A 2D finite element method is used to simulate the co-seismic process with a slip-weakening friction law and full inertial dynamics, and a linear viscoelastic model is used to calculate stresses during the interseismic loading process. In our branched fault models, a secondary planar fault intersects the main planar fault in the center of the main fault and divides the main fault into two segments. We find that the branched fault geometry causes the fault stress to depart from the regional stress field significantly over multiple earthquake cycles. Locally increased normal stress can slow down or stop rupture propagation, while locally reduced normal stress facilitates jumping (discontinuous) rupture between branches. The fault behavior also includes examples of ­øbackwards branching,­ñ where rupture propagates around the acute angle between the primary and secondary segments. Various types of events occur on our branched fault systems over multiple earthquake cycles, including 1) events that only rupture the favorable segment(s), 2) events that rupture part of the main fault and the secondary fault, and 3) events that rupture the entire fault system. The results of our study may have implications for understanding branching behavior in the three earthquakes above, and also may help to delineate the range of expected behaviors for branched fault systems in the future.
DE: 7260 Theory and modeling
DE: 7209 Earthquake dynamics and mechanics
DE: 7212 Earthquake ground motions and engineering
DE: 7215 Earthquake parameters
SC: Seismology [S]
MN: 2004 AGU Fall Meeting