Application of Vector-Type Super Computer to Understanding Giant Earthquakes and Aftershocks on Subduction Plate Boundaries

Abstract

In order to know why megathrust earthquakes have occurred in subduction zones such as the 2011 off the Pacific Coast of Tohoku Earthquake in Japan, we reconsider previous numerical simulation results and try to apply them to actual fields such as the 2004 Sumatra-Andaman earthquake and large interplate aftershocks of the 2011 Tohoku Earthquake. From this study, we propose that one of the possible reasons of pre-seismic change of the 2011 Tohoku Earthquake might have been smaller for its magnitude because its fault was composed smaller (M 7 class) asperities including the off Miyagi earthquakes as occurred in 1978 and 2005. We also suggest that the next megathrust earthquake along Nankai Trough in southwest Japan may have detectable pre-seismic change because it is composed of three large (M 8 class) asperities in Tokai, Tonankai and Nankai region. Our trial numerical simulation results by using vector-type super computer show that Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) may be useful to detect the pre-seismic change of a possible M 9 class coupled megathrust earthquake composed of Tokai, Tonankai, Nankai and Hyuga-nada asperities.