統計数理研究所

講演者: Rodolfo Console
(National Institute of Geophysics and Volcanology Rome, Italy)

講演題目: Renewal modeling and co-seismic stress transfer for seismic
hazard assessment in the Corinth Gulf, Greece, fault system

概要: Earthquake forecasts have always been a difficult task because they can be affected by uncertainty in terms of the most appropriate model and the involved parameter values. The models adopted in this study belongs to the category of the renewal models, based on the characteristic earthquake hypothesis, the necessary ingredients of which are a fixed geometry and the knowledge of the slip rate on the faults. Both the BPT and the Weibull distribution have been tested. The hazard rate so obtained is then modified by the inclusion of a permanent effect due to the Coulomb static stress change caused by failure of neighboring faults that occurred since the latest characteristic earthquake on the concerned fault. I apply this method along the Corinth gulf extension zone, a place that is rich with observations of strong-earthquake recurrence behavior, to assess their relative forecast applicability. The validity of the renewal models is assessed in retrospective way on the data of the last 300 years by comparison with a plain time independent Poisson model. This is done by means of statistical tools as the ROC diagram, the R-score and the log-likelihood ratio. I find that the renewal models perform better than the Poisson hypothesis. It seems also that the BPT distribution works slightly better than the Weibull distribution, while little advantage is achieved by the introduction of the Coulomb static stress change in the forecasting algorithm.