The Nucleation and Dynamic Rupture of Laboratory Earthquakes

Abstract:

We present the results of dynamic rupture experiments intended to mimic seismic rupture of faults.
The experimental device consists of a plate of polycarbonate in which a fault is cut at a critical angle, such that it produces stick-slip when it is submitted to uniaxal stress loading. The ruptures are visualized by photo-elasticity recorded with a high velocity camera. The radiated wavefield is studied with a network of acoustic sensors.

In a first part, we study the slow initiation of the rupture. We show that this stage actually consists of two phases, a long exponential growth followed by a catastrophic acceleration. The critical length and critical rupture velocity of the transition scale depend inversely on the normal stress; while the characteristic time is independent of the normal stress. We discuss these results with respect to recent observations of earthquake nucleation in natural faults.

In a second part, we will show that this experiment can be used to study the effect of barriers on a fault, as well as the effect on rupture propagation of a kink on a fault. We provide detailed observation of the wavefield radiated by the barrier, and compare it to the wavefield radiated by a kink. We compare the observations with theoretical results for the radiation of a barrier in a 2D in-plane geometry, and with 2D numerical simulations of rupture dynamics by the spectral element method.