Interactions and triggering in a 3‐D rate‐and‐state asperity model

Abstract

[1] We present a 3-D continuous quasi-dynamic rate-and-state model of multiple seismic asperities forced by surrounding aseismic creep and motivated by observations of coplanar multiplets. Our model allows to study the physics of interactions among a set of asperities. First, we show that the amount of interactions and clustering, characterized by the Omori law and interevent time distribution, depends on how far the system is from a critical density of asperities, which is related to the friction properties of the barriers separating the sources. This threshold controls the ability of a population of asperities to destabilize the creeping barriers between them and therefore determines whether dynamic sequences including several asperities in the same event might occur, in agreement with what is expected from observed magnitude-frequency distributions. Therefore, the concept of critical density of asperity provides a mechanical interpretation of statistical properties of seismicity. As an illustration, we used our numerical results in the specific case of Parkfield in the period preceding the M w 6, 2004 earthquake, in order to infer the steady state friction parameter (a -b) characterizing the creep of this part of the San Andreas Fault. We estimate a value of (a -b) that locally exceeds 0.001, which is in the upper range of what has already been proposed for the postseimic period of the M w 6, 2004 Parkfield earthquake.Citation: Dublanchet, P., P. Bernard, and P. Favreau (2013), Interactions and triggering in a 3-D rate-and-state asperity model,

Control of asperities size and spacing on seismic behavior of subduction megathrusts

“…Dublanchet et al [2013] used a model configuration made of several circular asperities embedded in a planar fault and identify a critical "asperities density" (defined as the amount of velocity weakening area with respect to the total fault area) needed to trigger a full fault rupture. Their study indicates that packed asperities favor the synchronization process.…”

“…Despite the simplicity of such models, fault segment interaction produces spatial and temporal complexity of seismic behavior [Huang and Turcotte, 1990;Ruff, 1992]. More advanced, fully dynamic numerical rupture simulations including the effects of both coseismic and dynamic stress transfer based on rate and state friction revealed important insights for seismic hazard assessment [Kaneko et al, 2010;Dublanchet et al, 2013].…”

Dynamics of a fault model with two mechanically different regions

“…We exclude simultaneous slip of the two regions (e.g. Dublanchet et al 2013;Yabe and Ide 2017), even though it could be easily treated by models describing the dynamics of faults with two asperities (e.g. Dragoni and Santini 2015;Dragoni and Tallarico 2016).…”

“…Kato (2004Kato ( , 2014 discussed the interplay between velocity-weakening and velocitystrengthening patches on a fault plane and the conditions for seismic and aseismic slip events. Dublanchet et al (2013) and Yabe and Ide (2017) considered a fault with a large number of asperities and pointed out that asperity concentration remarkably affects the slip behaviour of heterogeneous faults containing both velocity-weakening and velocity-strengthening regions: specifically, the entire fault may slip seismically if the asperity concentration exceeds a critical threshold. Bulk relaxation of the crust and the effect of pore fluid diffusion may also play a role.…”

Variations in precursory slip behavior resulting from frictional heterogeneity

“…Dublanchet et al (2013) and Yabe and Ide (2017) investigated the slip behavior of infinite-length planar and linear faults with periodic frictional parameter distributions, respectively. They reported a variety of slip behaviors, from seismic slip that ruptures only the velocity-weakening zone (VWZ) to seismic slip that ruptures the entire fault, including both the VWZ and velocity-strengthening zone (VSZ).…”