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Earthquake Rupture in Fault Zones With Along-Strike Material Heterogeneity

Yihe Huang

Published November 21, 2018, SCEC Contribution #8904

Geological and geophysical observations reveal along-strike fault zone heterogeneity on major strike-slip faults, which can play a significant role in earthquake rupture propagation and termination. I present 2D dynamic rupture simulations to demonstrate rupture characteristics in such heterogeneous fault zone structure. The modeled rupture is nucleated in a damaged fault zone and propagates on a preexisting fault towards the zone of intact rocks. There is an intermediate range of nucleation lengths that only allow rupture to spontaneously propagate in the damaged fault zone but not in a homogeneous medium given the same stresses and frictional parameters. Rupture with an intermediate nucleation length tends to stop when it reaches the zone of intact rocks for uniform fault stress conditions, especially when the rupture propagation distance in the damaged fault zone is relatively short and when the damaged fault zone is relatively narrow or smooth in the fault-normal direction. Pronounced small-scale heterogeneity within the damaged fault zone also contributes to such early rupture termination. In asymmetric fault zones bisected by a bimaterial fault, rupture moving in the direction of slip of faster rocks tends to terminate under the same conditions as in symmetric fault zones, whereas rupture moving in the direction of slip of slower rocks can penetrate into the zone of intact rocks. A sufficiently-large asperity located at the edge of the zone of intact rocks also allows break-through rupture. The results suggest the along-strike fault zone heterogeneity can play a critical role in seismicity distribution.

Citation
Huang, Y. (2018). Earthquake Rupture in Fault Zones With Along-Strike Material Heterogeneity. Journal of Geophysical Research: Solid Earth,. doi: 10.1029/2018JB016354.