Multi-physical couplings and microstructure size effects on the localization of deformation in a fault core

Hadrien Rattez, Ioannis Stefanou, Jean Sulem, Manolis Veveakis, & Thomas Poulet

Published August 15, 2018, SCEC Contribution #8682, 2018 SCEC Annual Meeting Poster #204

Seismic slip in the brittle part of the lithosphere is often accompanied by extreme shear strain localization into a narrow, thin zone, which is called Principal Slip Zone (PSZ). According to field observations, the PSZ has a finite thickness and varies from hundreds of microns to few centimeters. The size of this zone plays a major role in the mechanism of earthquakes as it affects the energy budget of the fault core and its stability.

We model here the creation of shear bands inside fault gouges considering the effect of microstructure by resorting to elastoplastic Cosserat continua and Thermo-Hydro-Chemo-Mechanical couplings. The use of Cosserat theory not only enables to regularize the problem of localization by introducing an internal length into the constitutive equations, but at the same time it introduces information about the size of the microstructure.

The results obtained with numerical simulations are compared with experimental and in situ observations for the shear band thickness and the fracture energy. It enables us to understand the role of various phenomena on the behavior of a fault, such as thermal pressurization, flash heating and the size of the microstructure, among others on the thickness of the band but also on the stability of the system.

Key Words
Strain Localization, fault mechanics, THM couplings, Finite Element modeling, microstructure, Cosserat continuum

Citation
Rattez, H., Stefanou, I., Sulem, J., Veveakis, M., & Poulet, T. (2018, 08). Multi-physical couplings and microstructure size effects on the localization of deformation in a fault core. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)