Episodic aseismic slip in a two‐degree‐of‐freedom block‐spring model

Abstract

We consider a two‐degree‐of‐freedom block‐spring model, in which two blocks (Block 1 and Block 2) are connected by a spring and driven by a slowly moving driver. Assuming a rate‐ and state‐dependent friction law, we set the friction parameters such that dynamic instability occurs at Block 1. Episodic aseismic slip occurs at Block 2 when its frictional parameters are near the stability transition. When the stress has accumulated to approximately a steady state level during an interseismic period, Block 2 starts a slow slip. Quasi‐static oscillation in the stress and slip velocity occurs with decaying fluctuation amplitudes leading to the steady state values. The decaying oscillation could be a plausible generation mechanism of the episodic aseismic slip observed in the Tokai district, Japan, since 2001. We also consider various slip modes on a plate boundary based on this two‐block model associated with the interaction between different frictional properties.

Complex Earthquake Cycle Simulations Using a Two-Degree-of-Freedom Spring-Block Model with a Rate- and State-Friction Law

“…This type of state evolution law was used in numerical simulations by YOSHIDA and KATO (2003), HE (2003) and ERICKSON et al (2008). Because the sliding behaviour and the condition for the occurrence of unstable slip are different for the two types of state evolution law (MARONE 1998;RANJITH and RICE 1999), the simulation results in the present study cannot be directly compared with those using the slip type of the state evolution law.…”

“…In this case, unstable slip is expected to occur at the ith block for k 0 ? k 12 \ k ci , where k ci is the critical stiffness of the ith block, as discussed by YOSHIDA and KATO (2003). When k 0 [ k ci , stable slip occurs at the ith block, whether or not the other block is locked.…”

“…The two-degree-of-freedom spring-block model used in the present study is the same as that used by YOSHIDA and KATO (2003), except for the evolution law. Two rigid blocks on a frictional floor are connected by a spring of stiffness k 12 , and each block is dragged (using a spring of stiffness k 0 ) by a driver moving at a rate V pl in the x direction (Fig.…”

“…Using the same twoblock model, HE (2003) examined the effects of the spring coupling stiffness on slip patterns; it was found that a higher stiffness tended to generate simpler slip patterns in the periodic recurrence of earthquakes, while more complicated or chaotic slip patterns occurred for a lower stiffness. YOSHIDA and KATO (2003) used a two-degree-of-freedom spring-block model to examine the interactions between a block with unstable frictional properties and a block with stable or conditionally stable frictional properties, and successfully explained the occurrence of slow earthquakes. In other work, MITSUI and HIRAHARA (2004) connected five blocks in series in order to simulate complex earthquake cycles along the Nankai trough; the five blocks represented the five segments in which earthquakes have historically taken place.…”

Recent developments in dynamic fracture: some perspectives

“…The possible roles of non-monotonic friction laws in naturally occurring slow earthquakes have been recently explored [186][187][188][189][190]. While other mechanisms for the emergence of slow rupture have also been proposed, they generally involve invoking other physical ingredients such as higher dimensionality, spatial variation of the friction law and stress heterogeneities [191][192][193], dilation and pore pressure effects [193], and a discrete description of asperities, including stochasticity of various local quantities [167].…”