Abstract
We investigate the effects of non-uniform distribution of constitutive parameters on the dynamic propagation of an earthquake rupture. We use a 2D finite difference numerical method and we assume that the dynamic rupture propagation is governed by a rate- and state-dependent constitutive law. We first discuss the results of several numerical experiments performed with different values of the constitutive parameters a (to account for the direct effect of friction), b (controlling the friction evolution) and L (the characteristic length-scale parameter) to simulate the dynamic rupture propagation on homogeneous faults. Spontaneous dynamic ruptures can be simulated on velocity weakening (a b) can arrest a dynamic rupture, but can be driven to an instability if suddenly loaded by the dynamic rupture front. Our simulations provide a picture of the complex interactions between fault patches having different frictional properties and illustrate how the traction and slip velocity evolutions are modified during the propagation on heterogeneous faults. These results involve interesting implications for slip duration and fracture energy.
Highlights
Modeling the dynamic propagation of earthquake ruptures requires the adoption of a constitutive relation, which governs the traction evolution within the cohesive zone (Ida, 1972; Andrews, 1976a; Okubo and Dieterich, 1984; Cocco and Bizzarri, 2002)
The goal of this study is to model the dynamic propagation of an earthquake rupture on a heterogeneous fault using RS constitutive laws
We present the simulation of the dynamic rupture propagation on a homogeneous fault model with a uniform distribution of constitutive parameters
Summary
Andrews, 1976a; Okubo and Dieterich, 1984; Cocco and Bizzarri, 2002). In particular, the Rate- and State-dependent friction laws (RS) derived from laboratory experiments (Dieterich, 1979a,b; Ruina, 1983) have been widely used in numerical simulations of earthquake ruptures, both at the laboratory scale (Bizzarri and Cocco, 2003 and reference therein) and for real-world faults (Guatteri et al, 2001, 2003). They have been applied to model preseismic and postseismic processes, such as earthquake nucleation (Dieterich, 1992; Lapusta and Rice, 2003) and afterslip (Marone et al, 1991) Another constitutive relation, the Slip-Weakening law (SW), is currently used in dynamic modeling of earthquake ruptures; according to this constitutive law the traction depends only on the slip (Ida, 1972; Andrews, 1976a,b; Ohnaka and Yamashita, 1989). Boatwright and Cocco (1996; BC96 in the following) discussed the frictional control of crustal faulting by using a RS law and a single degree of freedom spring-slider dynamic system They proposed that the fault response to the dynamic stress perturbations can differ depending on the variability of the constitutive parameters. We study how the interaction between velocity weakening and velocity strengthening portions of a 2D fault can affect the dynamic rupture propagation
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