ABSTRACT:

The physical processes which occur during an earthquake exhibit several coupled phenomena as large variations of stress, pore pressure and temperature take place in the slip zone. Thermo-poro-mechanical couplings due to shear heating can be associated to phase transition such as vaporization of the pore fluid, melting of fault gouge and to chemical effects such as dehydration of minerals or decarbonation of calcite. Different competing effects may influence dynamic slip and affect the weakening of the shear stress. In this paper, we show how thermal pressurization of the pore fluid and thermal decomposition of minerals induced by shear heating limit the co-seismic temperature rise which may explain the lack of pronounced heat outflow, and the lack of shallow frictional melting, along major tectonic faults.

1 INTRODUCTION

During the rupture of a fault, an earthquake occurs because the frictional resistance to slip on the fault walls decreases with increasing slip, causing an acceleration of sliding. To quantify the energy dissipated by an earthquake and assess the hazard of future ruptures, it is critical to understand the mechanics of slip weakening, i.e. how and how much fault friction drops in due course of the rupture. The physical processes which occur during an earthquake exhibit many coupled phenomena as large variations of stress, pore pressure and temperature take place in the material. Different competing effects may counter balance one another depending on the kinetics of the various physical processes.

2 MECHANISMS OF FAULT WEAKENING
2.1 Shear localization in faults

Field observations of mature faults, i.e. faults that have experienced a large slip, show a generally broad zone of damaged rock, but nevertheless suggest that shear in individual earthquakes occur in very narrow localized zones of few millimeters thick or even less.

This content is only available via PDF.
You can access this article if you purchase or spend a download.