HR: 0830h
AN: S41D-03    [Abstracts]
TI: Variations of Southern California Seismicity: Empirical Evidence and Possible Physical Causes
AU: Selva, J
EM: selva@bo.ingv.it
AF: INGV - Bologna, Via Donato Creti, 12, Bologna, BO 40128 Italy
AU: * Marzocchi, W
EM: marzocchi@bo.ingv.it
AF: INGV - Bologna, Via Donato Creti, 12, Bologna, BO 40128 Italy
AB: We investigate on the seismicity of Southern California in order to characterize its time evolution during last decades. We analyze the time series composed by the number of events per year, and the focal mechanisms of the earthquakes. The results show a statistically significant nonstationarity with a change occurred in the sixties, in both time series. The seismicity occurred before the change point is strictly linked to the San Andreas fault system; after the sixties, the seismicity appears to be more scattered in terms of focal mechanisms and location, and with a lower seismic rate. Finally, we provide a possible physical explanation of the significant nonstationarity by modeling the postseismic stress perturbation field induced by two giant earthquakes occurred in the sixties, the Chile (1960) and Alaska (1964) earthquakes. At a first order, the postseismic stress rate seems to be in agreement with the changes in seismicity observed, supporting a causality hypothesis. The model also foretells the future behavior of the trend of seismicity in Southern California. This (forward) prediction gives an important opportunity to validate the causal hypothesis of remote (and long-term) coupling between earthquakes.
DE: 7209 Earthquake dynamics and mechanics
DE: 7230 Seismicity and seismotectonics
DE: 7260 Theory and modeling
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8164 Stresses--crust and lithosphere
SC: Seismology [S]
MN: 2005 Joint Assembly