HR: 1340h
AN: S33C-1469    [Abstracts]
TI: Do repeating earthquakes talk to each other?
AU: * Chen, K H
EM: katepili2003@yahoo.com.tw
AF: Department of Earth Sciences,National Cheng Kung University, #1 Ta-Hsueh Rd., Tainan, 701, Taiwan
AU: Burgmann, R
EM: burgmann@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 211 McCone Hall, University of California, Berkeley, CA 94720-4760, United States
AU: Nadeau, R M
EM: nadeau@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 211 McCone Hall, University of California, Berkeley, CA 94720-4760, United States
AB: What determines the timing of earthquake recurrences and their regularity is of fundamental importance in understanding the earthquake cycle and has important implications for earthquake probability and risk estimates. This question cannot be answered without a statistically sufficient set of observations of recurrence properties in natural earthquake populations. Here we examine the distribution in space and time of a large dataset of repeating microearthquakes at Parkfield, California, that provide the opportunity to examine the degree to which these small ruptures communicate and influence each other's time of rupture. We find that 67% of quasi-periodic repeating sequences (i.e., coefficient of variation in recurrence interval less than 0.3) correspond to zones of low seismicity, suggesting that these quasi-periodic repeaters are more isolated in space and from perturbing stress changes. We find that closely spaced repeating sequences tend to have strong interaction in time, reflected in temporally clustered event recurrences. The temporal correspondence appears to be a function of separation distance from nearby earthquakes rather than the relative size of the events. The occurrence of large earthquakes can also have a strong impact on the interaction process. Accelerations of repeating sequences are associated with M 4-5 events that occurred in the mid-1990s. Following the 28 September 2004, M6.0 Parkfield, California earthquake, a large number of postseismic repeats occurred, where the sequences exhibit accelerated recurrence behavior following the mainshock. The characteristically decaying afterslip pattern is not obvious for some of the repeating sequences located close to the largest co- seismic slip area, whereas it is clearly seen in the repeating sequences at much greater distances from the rupture. Based on the above observations, we are able to model and test the extent to which fault interaction in the form of static stress changes and transient postseismic fault creep produces the observed aperiodicity in the occurrence of these events, and furthermore, attempt to improve predictions of the times of future event repeats.
DE: 0545 Modeling (4255)
DE: 8164 Stresses: crust and lithosphere
SC: Seismology [S]
MN: 2007 Fall Meeting