Dynamic rupture modeling of thrust faults with parallel surface traces.

Paul L. Peshette, Julian C. Lozos, & Doug Yule

Published August 15, 2017, SCEC Contribution #7783, 2017 SCEC Annual Meeting Poster #178

Fold and thrust belts (such as those found in the Himalaya or California Transverse Ranges) consist of many neighboring thrust faults in a variety of geometries. Active thrusts within these belts individually contribute to regional seismic hazard, but further investigation is needed regarding the possibility of multi-fault rupture in a single event. Past analyses of historic thrust surface traces suggest that rupture within a single event can jump up to 12 km. There is also observational precedent for long distance triggering between subparallel thrusts (e.g. the 1997 Harnai, Pakistan events, separated by ~50 km). However, previous modeling studies find a maximum jumping rupture distance between thrust faults of merely 200 m.

Here, we present a new dynamic rupture modeling parameter study that attempts to reconcile these differences and determine which geometrical and stress conditions promote jumping rupture. We use a community verified 3D finite element method to model rupture on pairs of thrust faults with parallel surface traces that dip either towards or away from each other. We vary stress drop and fault strength to determine which conditions produce jumping rupture at different dip angles and different separations between surface traces. In fault pairs that dip toward each other, we find that rupture is more likely to jump when the dip is steeper, while the opposite is true for fault pairs that dip away from each other. This parameter study may help to understand the likelihood of jumping rupture in real-world thrust systems, and may thereby improve earthquake hazard assessment.

Key Words
dynamic rupture modeling, thrust faults, jumping rupture, parameter study, stepover, triggered slip, fault geometry

Citation
Peshette, P. L., Lozos, J. C., & Yule, D. (2017, 08). Dynamic rupture modeling of thrust faults with parallel surface traces.. Poster Presentation at 2017 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)