HR: 0800h
AN: NG31A-0854    [Abstracts]
TI: A damage-mechanics model for crustal deformation
AU: * Nanjo, K Z
EM: nanjo@cse.ucdavis.edu
AF: Center for Computational Science and Engineering, c/o Department of Physics, University of California at Davis, One Shields Avenue, Davis, CA 95616 United States
AU: Turcotte, D L
EM: turcotte@geology.ucdavis.edu
AF: Department of Geology, University of California at Davis, One Shields Avenue, Davis, CA 95616 United States
AU: Shcherbakov, R
EM: roshch@physics.ucdavis.edu
AF: Center for Computational Science and Engineering, c/o Department of Physics, University of California at Davis, One Shields Avenue, Davis, CA 95616 United States
AB: The deformation of the brittle upper crust is primarily associated with displacements on faults. Nevertheless, it has often been found that continuum fluid models, usually based on a non-Newtonian viscosity, are applicable. We derive a continuum rheology for crustal deformation using damage mechanics. It is hypothesized that when a constant strain rate $\dot{\epsilon}$ is applied to a solid material the stress {\it $\sigma$} and damage increase until failure occurs, which is analogous to an earthquake. We further assume that this process is repeated, in analogy to the repetitive occurrence of earthquakes on a fault. Our model assumes that the crust behaves elastically below a yield stress {\it $\sigma$$_{y}$}. Above this stress the continuum deformations can be modeled as a non-Newtonian viscous flow with $\dot{\epsilon}$ $\sim$ ({\it $\sigma$}-{\it $\sigma$$_{y}$})$^{{\it n}}$ where {\it n} is constant. We derive the modified Omori's law for aftershock decay using a viscoelastic version of our model and get good agreement with observations taking {\it n} = 6. Using parameter values appropriate for aftershocks, we obtain a continuum crustal rheology that can explain major orogenies such as the Indian-Asian collision.
DE: 7230 Seismicity and seismotectonics
DE: 8020 Mechanics
DE: 8123 Dynamics, seismotectonics
DE: 8159 Rheology--crust and lithosphere
DE: 7209 Earthquake dynamics and mechanics
SC: Nonlinear Geophysics [NG]
MN: 2004 AGU Fall Meeting