HR: 0800h
AN: S11C-0708    [Abstracts]
TI: Comparisons between observed properties of aftershock sequences in southern California and predictions of a damage rheology model
AU: * Yang, W
EM: wenzheny@usc.edu
AU: Ben-Zion, Y
EM: benzion@usc.edu
AB: Aftershock sequences are commonly observed, but their properties vary from region to region. Ben-Zion and Lyakhovsky (2006) developed a solution for aftershocks decay in a damage rheology model. The solution indicates that the productivity and duration of aftershocks decrease with increasing value of a material parameter R given by the ratio of timescale for brittle deformation to timescale for viscous relaxation. The parameter R is inversely proportional to the degree of seismic-coupling and is expected to increase primarily with increasing temperature, and also with increasing thickness of sedimentary cover. To test these predictions, we use the relocated catalog of Lin et al. (2007) and analyze properties of aftershock sequences in the following five southern California regions. (1-2) The Coso and Imperial Valley areas with high heat flow. (3) The Landers and Hector- Mine region with low heat flow and thin sedimentary cover. (4-5) The San Bernardino Basin and Ventura Basin with low heat flow and thick sedimentary cover. In each region we consider events with magnitudes between 4.0 and 6.0 to be mainshocks. For each mainshock, we consider events to be aftershocks if they occur in the subsequent 50 days, within a circular region that scales with the magnitude of the mainshock and in the magnitude range between that of the mainshock and 2 units lower. This procedure produces 25-178 aftershock sequences in each of the five regions. We stack the aftershock sequences in each region and analyze the properties of the stacked data. The initial results indicate that the productivity and duration of the stacked aftershock sequences in the different regions increase in the following order: Coso, Imperial Valley, San Bernardino Basin and Ventura Basin, and the Landers and Hector-Mine area. These results are compatible with the damage model predictions. We are in the process of performing additional comparisons between the model predictions and observed data. Updated results will be presented in the meeting.
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Seismology [S]
MN: 2007 Fall Meeting