Dynamics of Non-planar Thrust Faults Governed by Various Friction Laws

Bin Luo, & Benchun Duan

Published August 15, 2017, SCEC Contribution #7710, 2017 SCEC Annual Meeting Poster #184

Fault interface topography is a prevailing factor in earthquake rupture dynamics. In subduction zones, large-scale oceanic reliefs such as seamounts and plateaus on the incoming oceanic plate can be subducted with the downgoing plate, giving rise to significant geometrical irregularities on the fault interface. Another key factor in controlling rupture dynamics is the friction law operating on the fault interface. Although rate- and state-friction laws have been proposed to behave similarly to the linear slip-weakening law on a planar fault model and produce an equivalent slip-weakening curve in dynamic rupture simulation, it remains unclear that whether dynamic rupture behavior governed by different functional forms of frictional constitutive laws would be affected by complex fault geometry in a similar manner.

We explicitly incorporate non-planar thrust fault geometry in a three-dimensional finite element model to perform numerical simulations of spontaneous dynamic rupture in order to compare the effect of large-scale seamount-like geometrical irregularity on earthquake rupture along a thrust fault interface governed by various friction laws, including linear slip-weakening friction law and rate- and state-dependent friction laws with different forms (e.g., aging law, slip law, and slip law with strong rate weakening). Our results show that the oceanic relief geometry could act as rupture barrier with its high strength area unfavorable for rupture propagation. There are three general types of rupture patterns associated with such a bumpy geometry regardless of which friction law is applied. The first one is that the rupture directly passes through the bump with minor impedance by the high strength area, causing slightly prolonged rupture duration. The second one is that part of the rupture is significantly obstructed by the bump, but the rest of the rupture manages to circumvent the high strength area, resulting in much longer rupture duration. The third one is that the rupture is completely stopped by the bump, limiting the size of the earthquake magnitude. The specific form of friction laws plays a critical role in varying the intensity of the rupture as well as the strength of the geometrical barrier to determine which type of rupture pattern should appear under certain prestress condition.

Citation
Luo, B., & Duan, B. (2017, 08). Dynamics of Non-planar Thrust Faults Governed by Various Friction Laws. Poster Presentation at 2017 SCEC Annual Meeting.

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