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Effects of Bimaterial Interface on Rupture Along Strike-Slip Branch Faults

Description: 

Crustal faults often separate material with differing elastic properties. Dissimilar media around faults has been shown to cause substantial effects on the rupture process along vertical strike-slip faults. Some previous studies suggest that asymmetry in wave propagation across a bimaterial interface can introduce normal stress perturbations on the fault around the rupture front that can lead to asymmetric bilateral or even unilateral rupture propagation. Furthermore, a bimaterial interface can also lead to differences in strain release across a fault interface for a fixed stress drop. Considering the effects caused by bimaterial interface on rupture propagation and also the fact that natural fault systems can be composed of numerous segments, it is worth understanding whether these effects can be significant enough to impact throughgoing rupture across a geometric complexity. Therefore, in this work we use dynamic rupture simulations with uniform tractions to investigate the effects of a bimaterial interface on rupture propagation along branch faults. To do this we construct a planar branch system which consists of a 40 km long main fault bisected by a 20 km secondary segment, at a branching angle of 50°. We assign a zone of stiffer material to one side of the fault system, such that both the main and secondary fault separate dissimilar media. We vary the material contrast (ɣ) from 0-0.20 in the zone of stiffer material such that the p-velocity in the stiffer material is Vp*(1+ɣ), where Vp is the p-velocity in the rest of the elastic medium. The results show that when rupture is nucleated on the main fault it is less likely to rupture the secondary segment as the material contrast increases if the main fault and secondary faults have the same sense of slip. If the faults have opposite senses of slip, we find that a larger material contrast promotes rupture propagation on the secondary fault. This could have implications for assessing seismic hazard in regions with complex fault systems which separate dissimilar media, in particular which direction seismic energy may be directed during an earthquake.

Session: Numerical Modeling in Seismology: Developments and Applications [Poster Session]

Type: Poster

Date: 5/1/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Evan

Student Presenter: Yes

Invited Presentation: 

Authors