Damage prediction of long-period structures during subduction earthquakes - Part 1: Long-period ground motion prediction in the Osaka basin for futureNankai Earthquakes -

摘要

The Nankai Trough earthquakes which are subduction earthquakes with magnitude greater than 8 have occurred at intervals of 90 to 150 years. The probability of earthquake occurrence within 30-years from January 1, 2008 are estimated at 60 70% and 50 % for the next Tonankai and Nankai earthquakes, respectively, showing very high possibility of the earthquake occurrence. It is very important to predict the long-period ground motions from the next Nankai Trough earthquakes for mitigating their disastrous effects. In this study, we show results of the prediction of future Nankai earthquake in Part 1 and the damage prediction map of high-rise buildings in the Osaka basin in Part 2. This paper (Part 1) focuses on the prediction of the long-period (>2.5s) ground motions in the Osaka basin during future Nankai earthquake using the 3D finite difference method and an earthquake scenario proposed by the Headquarters for Earthquake Research Promotion in Japan. The characteristics of the predicted long-period ground motions for the hypothetical Nankai earthquake are related with the geometry between the source and observation points, and with the thicknesses of the sediments of the basin. The duration of the long-period ground motions in an area located in the central part of the Osaka city is more than 4 minutes, and the largest peak ground velocities (PGVs) exceed 80cm/s. The predominant period is around 6 second. These results indicate the possibility of earthquake damage due to future subduction earthquakes in large-scale constructions such as tall buildings and oil storage tanks in the Osaka area.