Effect of Slip-Weakening Distance on Seismic–Aseismic Slip Patterns

Abstract

In order to explain the seismic-aseismic slip patterns observed on megathrust faults, numerical simulations were carried out using the quasi-dynamic asperity fault model with the slip-dependent friction and stress-dependent healing. Two friction law parameters, strength and slip-weakening distance, are interpreted in the subduction channel context. The parameters are treated as random fields with specified characteristics. Their distributions define heterogeneities of the interplate frictional coupling. The higher strength regions accumulate stresses, whereas the slip-weakening distance lengths control the stress release rates. The simulation results indicate that the slip-dependent asperity model reproduces key features of real megathrust fault behavior. First, stable and unstable slip movements can occur at the same locations, even if the friction parameters are fixed. Second, two rupture styles, single asperity breaks and wide, smooth, propagating rupture fronts, can be distinguished. The latter style is responsible for large slips near the free surface, where lower fault strengths are expected. The reason for these effects is that slip instabilities depend both on local friction and on the system stiffness, which is related to the slipping area size and distribution of slips. It is also shown that the high-strength interplate patches, such as subducted seamounts, can both promote and restrain large earthquakes, depending on the slip-weakening distance lengths.

Physicist in Search of the Theory of Earthquakes

“…The earthquake rupture processes can be simulated by using the differential-integral equation, where a slip velocity at a given point on a fault depends on the net stress, so the driving stress caused by the tectonic loading and slips or deformations in the whole medium, minus the frictional stress due to material characteristics of the fault at that point (Senatorski 2019). However, the seismicity models should involve probabilistic principles that reflect our uncertainty about the future earthquakes.…”

Features of the Largest Earthquake Seismic Cycles in the Western Part of the Aleutian Subduction Zone

“…The combination of seismic displacement regions with aseismic slip regions, usually observed along subduction interfaces, was explained in [46] based on a fault model and quasi-dynamic asperities with time-varying friction and the possibility of rupture healing depending on the stress level. The obtained results of numerical simulation reproduce the main characteristics of the behavior of a segment of the subduction zone.…”

Keyboard Model of Seismic Cycle of Great Earthquakes in Subduction Zones: Simulation Results and Further Generalization

“…Later, a set of mechanical models describing the generation of strongest earthquakes with the source length up to 1000 km was proposed assuming the idea of synchronous failure of several adjacent asperities: from a first simple model [3] to a very complex model by [4,5]. An explanation of seismic-aseismic slip patterns observed on megathrust faults proposed in [13] is also worth mentioning: the results of numerical simulations based on the quasi-dynamic asperity fault model with the slip-dependent friction and stress-dependent healing quite accurately reproduces the main features of real megathrust fault behavior.…”