Multi-hazard earthquake-tsunami loss estimation of Kuroshio Town, Kochi Prefecture, Japan considering the Nankai-Tonankai megathrust rupture scenarios

Abstract

The Nankai-Tonankai Trough is the primary source of major subduction earthquakes in western and central Japan, and the preparedness against future Nankai-Tonankai megathrust subduction events is of critical importance. This study develops a novel multi-hazard catastrophe model for the future Nankai-Tonankai megathrust subduction earthquake and tsunami based on a stochastic earthquake source modeling approach, and applies it to Kuroshio Town, Kochi Prefecture, Japan, that faces significant seismic-tsunami hazards due to the Nankai-Tonankai subduction earthquakes. The earthquake-tsunami catastrophe model incorporates the stochastic rupture sources, spatially correlated ground motion fields, tsunami inundation simulations, detailed building portfolio data, seismic and tsunami fragility models, and building damage cost estimation. It produces the multi-hazard and single-hazard loss distributions, accompanied by detailed earthquake rupture scenarios, shaking-tsunami hazard intensity distributions, and building damage distributions. The earthquake-tsunami loss estimation results for Kuroshio Town indicate that the tsunami loss tends to increase with the magnitude more significantly than the shaking loss and contributes more towards the increase in the multi-hazard total loss with the earthquake magnitude. Importanly, the new multi-hazard tool facilitates the identification of critical multi-hazard loss scenarios and leads to integrated hazard-risk maps that are particularly useful for disaster risk reduction and management purposes.