Jumping Rupture Between Parallel Thrust Faults - A Geometrical Parameter Study

William D. Kalman, & Julian C. Lozos

Submitted September 7, 2025, SCEC Contribution #14832, 2025 SCEC Annual Meeting Poster #TBD

Parallel pairs or networks of thrust faults often occur in convergent or transpressional tectonic settings, and understanding which conditions allow multi-fault rupture in such a setting is key for assessing hazard in these areas. In this study, we conduct dynamic rupture simulations on pairs of thrust faults that are completely parallel for their full downdip extent, varying their dip angles and the separation between them. The biggest influence on whether rupture can jump between the two faults is whether the earthquake nucleates on the hanging wall versus on the footwall of the second fault. For every dip angle we tested, a nucleation on the hanging-wall side allowed jumping rupture across wider separation distances. But, the specific pattern of which dip angles allow jumping ruptures at which distances also varies significantly according to which side of the fault system has the initial nucleation. For footwall-side nucleations, the relationship is a straightforward case of shallower angles allowing longer jumps. For hanging-wall-side nucleations, however, the pattern is more complex, with the shallowest and steepest dip angles allowing longer jumps, but intermediate angles suppress jumping rupture. We expect that this is related to whether the second fault is a on the compressional or extensional side of the first, but we are in the process of running additional simulations to see how this pattern persists under other initial stress conditions before we look deeper into the causes.

Key Words
thrust faults, reverse faults, dynamic rupture modeling, earthquake simulations, fault geometry, multi-fault rupture

Citation
Kalman, W. D., & Lozos, J. C. (2025, 09). Jumping Rupture Between Parallel Thrust Faults - A Geometrical Parameter Study. Poster Presentation at 2025 SCEC Annual Meeting.

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