Rupture propagation beyond fault discontinuities: significance of fault strike and location

Abstract

SUMMARY Earthquake rupture sometimes occurs on several faults, and often decelerates or terminates at fault stepovers. Factors that control the rupture processes across stepovers are important for an understanding of earthquake growth and termination. In this study, we investigate such factors by calculating the spontaneous rupture processes of two non‐coplanar faults in a 3‐D model. Dealing with two extreme models in which two strike‐slip faults are either parallel or perpendicular, we show that the rupture processes beyond fault discontinuities are drastically different for the two models. We find three factors influencing rupture processes beyond fault discontinuities: depth of the upper edge of the two faults, location of the edge of the first fault and geometry of the two faults. These factors determine the time and location of rupture jumps to the second fault. For rupture propagation to the second fault, it is essential for rupture on the first fault to arrive at the edge of the fault. In particular, whether rupture on the first fault reaches the Earth's surface or not controls the difficulty of rupture jumps and the locations where the rupture is triggered, which is also related to the step direction of the two faults. This is because the stress perturbation at the fault edge is affected by the Earth's free surface.

Earthquake Doublet Sequences: Evidence of Static Triggering in the Strong Convergent Zones of Taiwan

“…This result is similar to previous findings with respect to static stress triggering (e.g., King et al 1994;Stein et al 1994;Deng and Sykes 1997;Gomberg et al 1998;Stein 1999;Ammon et al 2008), rather than from dynamic triggering (Freed 2005). Alternatively, the triggering of 2 nd largest earthquake might be a result of rupture propagation beyond fault discontinuities (Kase and Kuge 2001;Duan and Oglesby 2006;Kase and Day 2006). However, the detailed relationship between the events in a doublet should be investigated further.…”

A Suite of Exercises for Verifying Dynamic Earthquake Rupture Codes

“…These two exercises examine the case of a stepover between parallel vertical right-lateral strike-slip faults (e.g., Kase and Kuge, 2001;Harris et al, 2002). Our group hypothesized that these fault-geometry benchmarks, which are simpler than the branched fault case would be an easier test of the codes, and this was indeed the situation, with qualitatively good matches occurring among the code results.…”

Effect of complex fault geometry and slip style on near-fault strong motions and static displacement

“…We may be able to ob-tain precise information on the fault segmentation if there are dense observation points (e.g., GPS reference points and control points) around the fault system. After constraining the fault geometry and slip distribution in this manner, we may be truly able to retrieve details of the rupture style; that is, the "dynamic source model" in recent literature (e.g., Beroza and Mikumo, 1996;Cotton and Coutant, 1997;Kase and Kuge, 2001). Since our approach can simultaneously compute static and dynamic motions near a fault system (Honda and Yomogida, 2003b), it will become a powerful tool in future to retrieve complex source processes with GPS as well as near-fault strong motion data composed of both static and dynamic components.…”