Spatio-temporal evolution of aftershock energy release following the 1989, MW6.9, LOMA Prieta earthquake in California

Abstract

We apply a stochastic model to study Benioff strain release after the Mw6.9 October 18, 1989 Loma Prieta strong earthquake in north California, USA. The model is developed, following a compound Poisson process and contours the evolution of strain release during the aftershock sequence following the main shock occurrence. First, the temporal evolution of the aftershock decay rate was modeled by the Restricted Epidemic Type Aftershock Sequence (RETAS) model and after that the recognized best fit model is integrated into the strain release stochastic analysis. The applied stochastic model of Benioff strain release empowers a more detailed study by detecting possible deviations between observed data and model. Real values of the cumulative Benioff strain release surpass the expected modeled ones, indicating, that large aftershocks cluster at the beginning of the Loma Prieta sequence immediately after the occurrence of the main shock. Strain release spatial analysis reveals release patterns, which change during the aftershock sequence.