MULTI-HAZARD SEISMIC AND TSUNAMI HAZARD ASSESSMENT IN OSAKA CITY CONSIDERING STOCHASTIC NANKAI-TONANKAI EARTHQUAKE SCENARIOS

Abstract

 We conducted a combined probability assessment of earthquake ground motion and tsunami damage for buildings in the entire city of Osaka, considering individual structure types. First, numerous finite fault models were synthetically generated along Nankai Trough. Each fault model has a different slip distribution with similar wavenumber characteristics to historical subduction earthquakes. Subsequently, strong-motion and tsunami simulations were performed for all generated fault models, and the dam-age probabilities to buildings in Osaka City were estimated. In estimating the damage probabilities, wooden and non-wooden buildings were distinguished. The spatial distributions of ground motion and tsunami damage probabilities showed different characteristics. Estimating damaged buildings at different magnitudes showed that the increase in the expected number of buildings damaged by tsunamis was significantly larger than that by earthquakes as the magnitude increased. Additionally, the combined damage probabilities of ground motion and tsunami damage were significantly different from the individual ones, indicating the importance of assuming both types of damage in coastal urban areas.