Slip‐behavior transitions of a heterogeneous linear fault

Abstract

Geological faults have frictional heterogeneity. Here we investigate the slip behavior of such heterogeneous faults in the simplest situation, simulating antiplane shear slip along an infinite linear fault in a 2‐D elastic model space, subjected to constant loading by external stresses characterized by stiffness and plate‐motion velocity. The fault is discretized into many subfaults, each of which has either a velocity‐weakening (VW) or velocity‐strengthening (VS) friction law. We vary the proportion of the fault that is VW, revealing several different regimes of slip behavior. The first regime boundary, where stick‐slip behavior is initiated, is located at the proportion of VW zones such that each VW zone reaches its nucleation size. The other boundary is located where the spatially averaged a − b value of the rate and state friction law is close to zero. Below this density, the VW zone slips seismically, whereas the VS zone shows afterslip. In contrast, above this density, the entire fault slips simultaneously at the seismic slip velocity. We observe transitional behavior at the second boundary, where relatively slower deformation dominates. We also explore the slip behavior of faults using Cantor‐set distributions of frictional parameters. We propose that frictional heterogeneity on the fault may explain not only the diversity of seismic phenomena but also the observed scaling of frictional parameters, such as slip‐weakening distance or the fracture energy of ordinary earthquakes.

Variations in precursory slip behavior resulting from frictional heterogeneity

“…Consistent with previous studies (e.g., Skarbek et al 2012;Dublanchet et al 2013;Luo and Ampuero 2017;Yabe and Ide 2017), we observed several different types of slip behavior in our parameter studies. The first is the "total seismic" regime, in which a mainshock event ruptures the entire seismogenic zone on the fault (parameter sets A-C in Fig.…”

“…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). Yabe and Ide (2017) documented slower deformation at the transition between two behaviors, which may correspond to slow earthquakes. In contrast, Skarbek et al (2012) documented transitions from seismic to slow slip on a finite frictionally heterogeneous fault.…”

“…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).…”

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.…”