Structural Research on the Nankai Trough Using Reflections and Refractions

To understand the megathrusut earthquake recurrence system around the Nankai trough southwestern Japan, the structural researches by seismic survey and observations will provide the significant information of megathrust earthquakes seimogenic zone. As previous structural researches, the subducting seamount in the Nankai earthquake seismogenic zone off Shikoku Island, the ridge subducting system in the Tokai earthquake seismogenic zone, splay faults in the Tonankai earthquake seismogenic zone and irregular structure in the boundary between the Tonankai and Nankai seismogenic zone off Kii peninsula. These structures and models are very important, significant and basical information to understand the recurrence system of megathrust earthquakes and rupture propagations. In this project, we will carry out seismic survey and tomography with dense arrays around the Nankai trough extending to off Hyuga sesimogenic zone. By 2004 Sumatra megathrust earthquake, we recognized such the large scale seismic linkage as 1960 Chile megathrust earthquake. Therefore, we will image large detailed large scale structures to understand structural components around the Nankai trough with off Hyuga area. Finally, we will construct the advanced structure model and develop the crustal medium model in close cooperation with other structural researches in this project. Based on these models, simulation and disaster mitigation researches will progress conspicuously.