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Effects of Dip Angle on Rupture Propagation Along Branch Fault Systems

Description: 

An important consideration in assessing seismic hazards is determining what is likely to happen when an earthquake rupture encounters a geometric complexity such as a branch fault. Previous studies showed parameters such as branch angle, stress-orientation, and stress heterogeneity as key factors in the self-determined rupture path on branch faults. However, most of these studies were conducted in 2-D space or in 3-D with perfectly vertical faults. Many natural strike slip faults do not form perfectly vertical and have some dipping angle. In this study, we investigate the effects of dipping angle on rupture propagation along a branch fault system. We construct 3-D finite element meshes where we vary the dip angles (9 geometries in total) of the main and secondary faults, the stressing angle (Ψ = 20°, 40° and 65°) and the hypocenter location with nucleation on both the main and secondary segments. We find that for intermediate stressing angle (Ψ = 40°), a rupture on the main fault is most likely to propagate across the branch intersection when the secondary fault is dipping. Also, for high stressing angle (Ψ = 65°), a rupture on the secondary fault is most likely to propagate to the main fault when the secondary fault is shallowly dipping. This is caused by a fast rupture speed on the secondary fault and the dynamic stress effect that develop with the interaction of the free surface and the dipping secondary fault. These results indicate that dip angle is an important parameter in determination of rupture path on branch fault systems, with potentially significant impact for seismic hazard and should be taken into account in future earthquake modeling.

Session: Numerical Modeling in Seismology: Developments and Applications - II

Type: Oral

Date: 5/1/2024

Presentation Time: 11:15 AM (local time)

Presenting Author: Evan

Student Presenter: Yes

Invited Presentation: 

Authors