[S09] PM-1

[S09-24] Nonstationary ETAS model: How it works for external forcing

*Takao KUMAZAWA¹, Yosihiko Ogata¹ (1. The Institute of Statistical Mathematics)

The stationary ETAS (epidemic type aftershock sequence) model is based on important empirical laws in aftershock statistics with a self-similar feature, and is therefore useful for the statistical analysis of many common earthquake occurrence series. However, as earthquake catalogs become richer, the non-stationarity arising from geophysical heterogeneity becomes more pronounced. This presentation discusses the utility of a model that assumes time dependence of the first two ETAS parameters, which are sensitive to the short-term prediction. The inversion analyses of the nonstationary ETAS model show heuristic results for swarm earthquakes and complex mainshock-aftershock-type seismicity. The case studies demonstrate how these parameters change quantitatively in swarm seismicity associated with slow slips, increases in pore fluid pressure such as magma and hydrothermal fluids, stress changes associated with earthquake motion, and interseismic induced effects due to geological properties.