Mechanisms and Definitions of Supershear Rupture

Abstract:

Supershear rupture propagation (i.e., the propagation of an earthquake rupture at a speed higher than that of the shear wave) can have important implications for ground motion, and it also can shed light on the physical conditions and processes taking place during earthquakes. There are many different mechanisms that can lead to the propagation of rupture at supershear speed, including the Burridge-Andrews mechanism that depends on the level of stress on the fault, mechanisms that depend on the presence of heterogeneities like stress barriers, fault bends, and stepovers, and a mechanism that depends on wave conversions at the Earth’s free surface. In this presentation we give an overview with examples of some of these mechanisms, and discuss potential implications for the prevalence and observability of supershear rupture. We also discuss recent work on how different means of defining or calculating rupture speed in a numerical model may lead to different classifications of earthquakes as either supershear or subshear, and how this distinction may shed light on observational characteristics of supershear rupture.