Shear Transformation Zone Theory in a Model of Seismic Slip:
Energetics of Strain Localization
Ann Hermundstad
Department of Physics, UCSB
Santa Barbara, CA 93106
Date: 04/18/2011
Abstract
Developing quantitative methods for partitioning released strain energy between different
processes during earthquake rupture remains a longstanding and fundamental issue in
seismology. The discrepancy between laboratory-based predictions and field measurements of
surface heat flow motivates the development of a quantitative approach to partitioning dissipated
energy in sheared amorphous materials on both the laboratory scale and the seismic scale. In this
talk, I will discuss theoretical methods used to quantify the energy dissipated to heat and to local
disorder in a sheared layer of granular fault gouge. Local disorder is modeled using Shear
Transformation Zone (STZ) Theory, a continuum model of non-affine deformation in amorphous
solids that quantifies local configurational disorder and resolves spontaneous localization of
strain. I will show that changes in configurational disorder play a significant role in dissipation,
providing a mechanism for strain localization and thereby dissipating energy that is traditionally
attributed to heating and fracture.