GEOMETRIC EFFECTS ON EARTHQUAKE NUCLEATION ON BENT DIP-SLIP FAULTS

Abstract

The geometric effects on earthquake nucleation processes on bent dip-slip faults are studied using a slip strengthening and weakening friction law implemented in a two-dimensional quasi-static boundary integral model. The results show that the bend causes normal stress variations under tectonic loading on both the upper and lower segments. These stress variations differ from those on planar faults, leading to significant effects on earthquake nucleation location and time. Earthquakes tend to nucleate at shallower locations on thrust faults and at deeper locations on normal faults for steeper dipping angles on the lower fault segments. The elapsed time until nucleation on both thrust and normal faults is increased considerably as the bend angle becomes larger. For a thrust fault with a nearly horizontal lower segment, the time until nucleation can be more than 10 times larger than that for a corresponding planar fault. These findings may provide important insights for earthquake hazard analysis by taking the fault geometry effect into account when estimating hypocenter positions and time to instability.