SENSITIVITY ANALYSIS OF FAULT PARAMETERS FOR TSUNAMI HEIGHT ALONG THE WEST COAST OF JAPAN WITH STOCHASTIC SOURCE MODELS

Abstract

 This study aims to quantify the sensitivity of fault depth and rake to the coastal tsunami height. The target earthquake source is the subduction zone along the Nankai Trough, conditioned on the southwest of Japan. First, possible ranges of the fault parameters are investigated. The spatial distribution of fault depth is compared using existing two major fault models, Slab2 and the Cabinet Office of Japan. Regarding the rake angle, a statistical analysis is conducted using historical earthquake catalogs. Second, the numerical tsunami simulation for many hypothetical source models is conducted. Different eight patterns of fault depth and rake angle with the same slip distributions are considered. Each pattern contains 100 source models with a moment magnitude of 9.1, thus, 800 tsunami simulations in total are performed. At coasts facing the open sea, the median tsunami heights between 100 scenarios with 5 km deeper faults were 1 m larger than those with the original depth of the existing model. And at same coasts, the median tsunami heights between 100 scenarios with rake rotated -14.5 degrees were 0.4 m larger than those with the original rake of the existing model.