Coseismic slip gradient and rupture jumps on parallel strike slip faults

Zaifeng Liu

Accepted September 21, 2015, SCEC Contribution #6024

Field observations of slip distribution along large strike-slip faults and preliminary rupture model simulations reveal a possible correlation between slip gradient near a fault end and the ability of a rupture to jump over a structure stepover in a strike-slip fault system. We simulate the dynamic rupture process on two parallel strike slip faults imbedded in an elastic medium to investigate this correlation and compare model-generated results with field-measured data. We find that the slip gradients calculated over the final 1 km of a fault have a linear relationship with both the average stress drop on the fault and the largest width of the step that could be jumped by a propagating rupture. Our dynamic Coulomb stress analyses show that the average stress drop on the first fault, which is proportional to the slip gradient in the final 1 km, determines the positive Coulomb stress region at the end of the first fault, which in turn determines the largest jumpable step width. A larger stress drop results in a larger positive Coulomb stress region around the first fault end, which allows the rupture to jump a wider stepover.

Key Words
Coseismic slip gradient, rupture jumps, parallel strike slip faults

Liu, Z. (2015). Coseismic slip gradient and rupture jumps on parallel strike slip faults. Bulletin of the Seismological Society of America, (accepted).