UC Davis

The geometry of a strike-slip fault system is an important component that influences the kinematics and interactions of the various faults within the system. Discontinuities and bends in the fault geometry not only determine the types of structures and the physiography that we observe along the fault system but also have a significant influence on the propagation of earthquake ruptures. A precise knowledge of the fault geometry, especially how it is segmented and other physical parameters, is essential for seismic hazard analysis. It is known that earthquake ruptures sometimes propagate over multiple faults by jumping from one segment to the next. A fault jump is a sudden dynamic coalescence of two faults separated by a step-over. Field observations suggest that a step-over width of 5 km is an appropriate maximum jump distance. Our study shows that between 2.5 and 6.5 km of step-over width, the probability of fault jump, for both releasing and restraining step-overs, decreases significantly from 100 to <10 %.