Dynamics of Nonplanar Thrust Faults Governed by Various Friction Laws

Abstract

Large‐scale irregular geometry of a fault surface, such as seamounts and subducted oceanic plateaus, is a prevailing factor that introduces stress heterogeneity and affects rupture dynamics. However, dynamic ruptures are also controlled by the constitutive laws that describe how fault friction evolves. In this study, we explicitly incorporate nonplanar thrust fault geometry into a three‐dimensional finite element model to numerically simulate spontaneous dynamic rupture and explore how dynamic ruptures would behave on a nonplanar fault surface under the influence of different friction laws. Our results show that a subducted oceanic relief (a bump) could act as a rupture barrier with its high strength area being unfavorable for rupture propagation, and such a geometrical effect varies with the dimension of a bump. When a bump is too high, the dynamic rupture is completely arrested. When the bump is too low, the rupture is barely affected. When the bump is of an intermediate height, the rupture is obstructed by the bump and splits into two parts, which circumvent the high strength area of the bump and then converge on the other side, triggering a strong slip velocity pulse. The relation between these rupture behaviors and bump geometry under a given prestress condition varies with the specific forms of friction law, which determines how fast a rupture releases energy and how strong a bump can be as a barrier.

Deriving Rupture Scenarios From Interseismic Locking Distributions Along the Subduction Megathrust

“…However, these effects are not considered in this study, as their relevant parameters on the megathrust are poorly known and we do not know whether such mechanisms occurred during the Nicoya earthquake. Furthermore, numerical results based on velocity‐weakening law do not qualitatively differ with those using slip‐weakening law (Gabriel et al, ; Luo & Duan, ; Murphy et al, ). As such, our results derived from the linear slip‐weakening law should be, at least qualitatively, no different from those incorporating more complex effects, if relevant frictional parameters on the megathrust can be well constrained from independent observations.…”

Rupture Dynamics of the 2012 Nicoya Mw 7.6 Earthquake: Evidence for Low Strength on the Megathrust

“…It has been found that models using rate‐weakening laws do not qualitatively differ with those using the LSW law (Bizzarri et al, 2001; Luo & Duan, 2018). However, friction laws with exponential weakening curves result in a faster energy release at the onset of slip and therefore may produce slightly more energetic rupture fronts than may those based on the LSW law (Dunham, 2007; Luo & Duan, 2018; Ryan & Oglesby, 2014). If we adopt a rate‐weakening friction law to reproduce the rupture process of the 2012 Nicoya M w 7.6 earthquake, a slightly higher yield stress may be inferred.…”

Dynamic Rupture Simulations of the 2008 Mw 7.9 Wenchuan Earthquake by the Curved Grid Finite‐Difference Method

“…In fact, geometrical complexity including steps (Duan & Oglesby, ; Harris et al, ; Hu et al, ), kinks (Kase & Day, ; Templeton et al, ), branching (Bhat et al, ; Kame et al, ), and roughness (Fang & Dunham, ; Luo & Duan, ; Yang et al, ) is common for earthquake faults in nature. The heterogeneities of fault surfaces, even small geometrical perturbations on planar faults, result in different dynamic rupture processes and then seismic radiation (Madariaga, ).…”