Poster #146, Fault and Rupture Mechanics (FARM)

Dynamic Interactions Between the Southern San Andreas Fault and Normal Faults in the Brawley Seismic Zone

LUIS I. BAZAN FLORES, Christodoulos Kyriakopoulos, David D. Oglesby, Aron J. Meltzner, Thomas K. Rockwell, & John M. Fletcher
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Poster Presentation

2021 SCEC Annual Meeting, Poster #146, SCEC Contribution #11420 VIEW PDF
In this work, we investigate the initiation phase and subsequent triggering of the Southern San Andreas Faut (SSAF) by adjacent smaller faults that could serve as nucleation points and/or participate in larger multi-fault ruptures. Our target area of investigation is the Brawley Seismic Zone (BSZ), which is characterized by intense micro-seismicity and seismic swarm sequences. The seismic activity mainly occurs along vertical left-lateral strike-slip cross faults that intersect the SSAF at several locations south of Bombay Beach, CA. However, there is also evidence that displacement in the northern BSZ occurs along normal faults (Brothers et al., 2009, Brothers et al., 2011) under the Salton... Sea, which could also interact with the SSAF. For these reasons, both the cross-faults and the normal faults in this area should be considered as potential initiation structures as well as faults participating in future multi-fault earthquakes. Here we extend our previous work regarding the dynamic interactions between the SSAF, the Imperial Fault (IF), and the system of cross faults (Kyriakopoulos et al., 2019) to include the possible interaction between the SSAF and a normal fault under the Salton Sea. To achieve our goal, we generated a series of dynamic rupture scenarios that help us illuminate the following: a) the mechanisms by which SSAF events can transfer slip onto the normal faults; and b) how normal fault earthquakes could trigger a major event on the SSAF. Preliminary results indicate that in the case of ruptures initiating on the SSAF, the nucleation location plays a determining role in the triggering of slip on the normal fault. More specifically, ruptures with nucleation location north of the normal fault (north to south propagation) generate more favorable conditions as opposed to ruptures with nucleation to the south (south to north propagation) and along the SSAF extension south of Bombay Beach.