HR: 17:30h
AN: S32F-07    [PDF]
TI: Expected Spatio-temporal Aftershock Patterns for Different Tectonic Regimes
AU: * Miller, S A
EM: steve@erdw.ethz.ch
AF: Institute of Geophysics, ETH-Hoenggerberg, Zurich, 8093 Switzerland
AB: Co-seismic damage created through shear rupture provides a high permeability fracture zone through which high pressure fluid pulses can propagate. In regions where fluids are trapped at high pressure by a geologic seal, the co-seismic rupturing of that seal allows the instant communication of high (lithostatic) and low (hydrostatic) pressure regions. The amplitude of the pressure difference depends on the depth but can be very large (for example, the difference is 170MPa for a trapped source at 10 km). The propagation of such a large pressure pulse will open fractures in the damage zone, travel at very high velocity, and trigger aftershocks by significantly reducing the effective normal stress in the regions through which it propagates. If aftershocks are driven by this mechanism, then aftershock distributions in space and through time should show a spatial distribution that depends on the type of faulting. Expected aftershock distributions are shown from modeling results for strike-slip, normal, and thrust fault events. The pressure pulse is modeled as a non-linear diffusion process where permeability is a strongly non-linear function of the effective normal stress acting on fractures. Results are compared with measured aftershock sequences.
DE: 7209 Earthquake dynamics and mechanics
DE: 7230 Seismicity and seismotectonics
DE: 7260 Theory and modeling
SC: Seismology [S]
MN: 2003 Fall Meeting