New Research Project For The Next Nankai Trough Mega Thrust Earthquakes -Towards To Understanding The Next Mega Thrust Earthquakes. And Mitigation Damages-

In the Nankai trough, mega thrust earthquakes are occurring with an interval of 100-200 years. So, many researches are focusing on the Nankai trough to elucidate the recurrence system of mega thrust earthquakes. The recent result of recurrence cycle simulation indicates the difference patterns and intervals of mega- thrust earthquake recurrences in each cycle. However, these results are not satisfied for the evaluation and estimation of next mega thrust earthquakes, so, we have to improve the structure model and the recurrence cycle simulation model with higher reliabilities. Especially, the estimation of recurrence cycle between the Tonankai and Nankai earthquake is very important for disaster preventions. Furthermore, the estimation of in coupled mega thrust earthquake around the Nankai trough such as Sumatra earthquake 2004 will be analyzed. To understand and estimate the next mega thrust earthquakes with detail structures and improved simulation model. We will propose research plan as follows, 1) Construct the detailed crustal medium around the Nankai trough using controlled sources and seismic tomography using dense seismic lines and OBS network arrays. 2) Observations of crustal activities around the Nankai trough and north eastern Japan. 3) Construct the database of long term plate coupling dynamics. And study the diversity of recurrence pattern and scale of next mega thrust earthquakes. 4) Develop the advanced simulation methods. 5) Improve the large scale recurrence cycle simulation model based on theoretical and experimental analyses. 6) Evaluate the precise strong motions and tsunamis for the disaster prevention. 7) Develop the reliable risk management system for next mega thrust earthquake. 8) Develop and contract the real time monitoring system around Kii peninsula. 9) Apply scientific results of Nankai seismogenic zone drilling to recurrence cycle simulation. The simulation research consists of the following five research groups. 1) Construction of database for spatiotemporal evolution of slip on the plate interface in the last 120 years. 2) Construction of database for diversity in the historical Nankai trough great earthquake sequences during several thousand years. 3) Development of advanced simulation methods. 4) Simulation research on factors controlling rupture mode of fault segments. 5) Construction of improved physical simulation model reproducing and predicting large diversity in long-term earthquake cycles. In order to understand the strong ground motions and tsunami expecting for future Nankai trough earthquake in detail for mitigation of possible disasters, we need study ground motions and tsunami from the former events occurred in 1944 and 1946 in detail. We will therefore conduct a computer simulation of strong ground motion and tsunami from the 1944 and 1946 events to reproduce strong ground motion and tsunami from the earthquake. We will modify structural model of elastic properties especially for the shear wave speed (Vs) and quality parameters (Q) that are rather difficult to investigate from geophysical explorations. The results of computer simulation for future Nankai trough earthquake are then used for 1) developing a realistic tsunami hazard map, 2) detail understanding of the damage of tall buildings and other important facilities, and 3) the planning of evacuation and recovery from the strong motion and tsunami disasters.