HR: 09:15h
AN: NG31A-06    [Abstracts]
TI: On the Excitation and Decay of Aftershocks
AU: * Turcotte, D L
EM: turcotte@geology.ucdavis.edu
AF: Department of Geology, University of California, One Shields Ave., Davis, CA 95616 United States
AU: Shcherbakov, R
EM: roshch@cse.ucdavis.edu
AF: Center for Computational Science and Engineering, University of California, One Shields Ave., Davis, CA 95616 United States
AB: Assuming the validity of the Gutenberg-Richter scaling, Bath's law, and the modified Omori's law for aftershocks, a generalized Omori's law is derived. This includes two characteristic times τ and c. The characteristic time τ is the time interval before the first aftershock occurs, the characteristic time c is the time when power-law decay and Gutenberg-Richter scaling are established. We have applied our scaling to a number of well documented aftershocks sequences with main shock magnitudes between 6 and 9. We fit the modified law for a range of lower magnitude aftershock cutoffs. We find that while τ is approximately constant, c has a strong dependence on the cutoff magnitude. The time delay is systematically greater for small magnitude aftershocks. We have also shown that the power-law decay of aftershock activity can be explained by damage mechanics. The main shock transfers stresses to some adjacent regions. As a result the excess stress above a crustal yield stress relaxes due to the aftershock activity. The resulting parameter values are consistent with other aspects of seismicity.
DE: 4430 Complex systems
DE: 4475 Scaling: spatial and temporal (1872, 3270, 4277)
DE: 7209 Earthquake dynamics (1242)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7260 Theory
SC: Nonlinear Geophysics [NG]
MN: Fall Meeting 2005