The role of porosity evolution and fluid flow in frictional instabilities: A parametric study using a spring-slider dynamic system

Abstract

We have investigated the role of porosity evolution and fluid flow in frictional instabilities by analyzing the response of a single degree of freedom dynamic system. The spring slider is governed by rate- and state-dependent constitutive law. We also account for effective normal stress changes caused by thermal pressurization with constant or variable porosity. Our simulations show that the stress drop during dynamic instabilities depends on constitutive parameters, porosity evolution, fluid flow as well as on the effective fault zone thickness, defined in this study as the ratio between the nominal thickness of the fault zone (w) and the hydraulically activated layer (why). Both porosity evolution and fluid flow can avoid the extremely large stress drop values inferred by thermal pressurization models and provide an attempt to reconcile them with seismological observations.