MODELLING THE ENERGY RELEASE PROCESS OF AFTERSHOCKS

Abstract

A stochastic model for the study of Benioff strain release during aftershock sequences is suggested. The stochastic model is elaborated after a compound Poisson process and is applied on data of the M7.1 Ocober 18, 1989 Loma Prieta aftershock sequence in northern California, USA. The temporal evolution of the number of events is first modelled by the Restricted Epidemic Type Aftershock Sequence (RETAS) model and then the identified best fit model is incorporated in the energy release analysis. The suggested model is based on the assumptions that there is no relation between the magnitude and the occurrence time of an event first and second, that there is no relation between the magnitude of a certain event and magnitudes of previous events. The obtained results from the examination of the energy release reveal that the suggested model makes a good fit of the aftershock Benioff strain release and enables a more detailed study by identifying possible deviations between data and model. The real cumulative energy release values surpass the expected model ones, which proves that aftershocks, stronger than forecasted by the model, are clustered at the beginning of the Loma Prieta sequence.