TEMPORAL CHANGE OF SEISMIC LOAD BY PROBABILISTIC SEISMIC HAZARD ANALYSIS WITH RENEWAL PROCESS

Probabilistic seismic hazard analysis (PSHA) is carried out during the seismic design of structures, and a seismic load corresponding to a certain return period is calculated. In PSHA, there are cases where a renewal process is adopted for some large specific earthquakes. When the probability of the occurrence of an earthquake increases within a certain period, the seismic load based on PSHA also increases. Here, we study the temporal change of the seismic hazard and the influence of the epistemic uncertainty on the occurrence probability of a large earthquake around Japan. When calculating the occurrence probability of earthquakes around the Nankai Trough and the Sagami Trough, the occurrence history is not clearly known, hence, a large epistemic uncertainty arises about the parameters of the Brownian Passage Time (BPT) distribution, such as the average recurrence interval, and the aperiodicity parameter alpha. In order to consider such uncertainty, we employ the Monte Carlo method with a large number of input parameters to grasp the temporal change of the occurrence probability. In addition, the calculated occurrence probability is incorporated into the seismic hazard analysis. Here, we conduct a risk assessment for sample sites and discuss the notion that the influence of the epistemic uncertainty on seismic loads varies greatly from one region to another.