The Nucleation and Dynamic Rupture of Laboratory Earthquakes

Tuesday, 16 December 2014: 2:25 PM
Soumaya Latour1, Alexandre Schubnel1, Stefan Bjorklund Nielsen2, Raul I Madariaga1, Jean Paul Ampuero3 and Sergio Vinciguerra4,5, (1)Ecole Normale Supérieure Paris, Laboratoire de Géologie, Paris, France, (2)University of Durham, Durham, United Kingdom, (3)California Institute of Technology, Seismological Laboratory, Pasadena, CA, United States, (4)University of Leicester, Leicester, United Kingdom, (5)British Geological Survey Keyworth, Nottinghamshire, United Kingdom
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.