Tsunami Simulations in the Western Pacific Ocean and East China Sea from the Great Earthquakes Along the Nankai-Suruga Trough

Abstract

Tsunamis from great earthquakes can travel long distances and still cause damage when they strike, as was demonstrated by the March 11, 2011 Tohoku earthquake (Mw 9.1) which attacked a number of Pacific Ocean coasts. Along the Nankai-Suruga trough, great interplate earthquakes (M>8) have recurred historically, and the occurrence of another great earthquake can be expected in the near future. Great earthquakes along the Nankai-Suruga trough also generate large tsunamis in the western Pacific Ocean and East China Sea. In this study, we carried out tsunami numerical simulations in the western Pacific Ocean and East China Sea using existing static fault models of Tokai and Nankai earthquakes since AD 1498. Tsunami propagations were computed by use of non-linear long-wave equations, including the Corioli’s force using the GEBCO 1-min bathymetry data, for a 24-h period after the earthquakes. The results of our simulations show the following: Tsunami heights in the studied oceans depend primarily on the slip amounts on the Nankai fault and are insensitive to the Tokai fault. Tsunamis from the Nankai earthquakes enter the East China Sea through the Tokara Strait, but the tsunami heights along the east coast of China were less than 1.0 m. Delayed slip on faults significantly affects the tsunami heights in the ocean areas studied. Tsunami heights computed using the 1707 and 1854 Nankai fault models were higher than those obtained from computations of other events. The tsunami behaviors computed in our study may correspond to the water disturbances recorded in Chinese historical documents on the dates of the 1707 Ho’ei and 1854 Ansei-Nankai earthquakes. However, the simulations show that tsunami heights along the east coast of China remain small when the assumed 1605 narrow-width fault model is used.