Towards the understanding of mega-thrust earthquake occurrence system around southwestern Japan -Developing and utilization of the dense ocean floor observatory-

摘要

The Nankai Trough in Southwestern Japan is well known as the mega thrust earthquake generating tsunamis, with the interval of 100-150 years. The 1944 Tonankai and the 1946 Nankai earthquakes around the Nankai trough, each hypocenter was located off the Kii peninsula in southwestern Japan. Based on crustal structure and simulation researches, we proposed and have been starting to deploy the dense ocean floor observatory network system around the Tonankai seismogenic zone, to monitor crustal activities using broadband seismometer, accelerometer and precise pressure gauges. The ocean floor network is significant ant important to monitor the crustal activities around mega-thrust earthquakes. Furthermore, this system will contribute to early warning of earthquakes and tsunamis.