Modeling the dynamic rupture propagation on heterogeneous faults with rate- and state-dependent friction

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) fault patches: our results point out the dependence of the traction and slip velocity
evolution on the adopted constitutive parameters. We therefore model the dynamic rupture propagation on
heterogeneous faults. We use in this study the characterization of different frictional regimes proposed by
Boatwright and Cocco (1996) based on different values of the constitutive parameters a, b and L. Our numerical
simulations show that the heterogeneities of the L parameter affect the dynamic rupture propagation, control
the peak slip velocity and weakly modify the dynamic stress drop and the rupture velocity. Moreover, a barrier
can be simulated through a large contrast of L parameter. The heterogeneity of a and b parameters affects the
dynamic rupture propagation in a more complex way. A velocity strengthening area (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.