[S-CG57] Structure and evolution of Japanese islands - Formation of island arc systems and earthquake cycles

[SCG57-P05] 3D velocity model in the region of Nankai Trough

*Minako KATSUYAMA¹, Ayako Nakanishi¹, Rei Arai¹, Shigeyoshi Tanaka¹, Narumi Takahashi², Hiromi Kamata¹, Yoshiyuki Kaneda³ (1.Japan Agency for Marine-Earth Science and Technology, 2.National Research Institute for Earth Science and Disaster Resilience, 3.Kagawa University)

Keywords:3D velocity model , Nankai Trough, subduction zone

This is a part of the project “Comprehensive evaluation of faults information on offshore Japan”, by the Ministry of Education, Culture, Sports, Science and Technology (MEXT). The project consists of three themes, 1) Collecting seismic survey data and building a database of offshore faults, 2) Interpreting distribution of active faults using seismic data collected, and conducting the seismic re-processing by leading-edge seismic technology for the seismic data obtained in previous decades, 3) Building the fault models for a simulation of strong motion and tsunami disaster, based on the interpreted faults. Our purpose of this study is make a 3D velocity model in the Nankai Trough to provide with the support we needs to interpret faults.
The Nankai Trough, where the Philippine sea plate is subducting beneath the Eurasian plate. Some seamounts and ridges are subducted here.
3D velocity model was constructed by seismic data and ocean bottom seismometer(OBS) refraction survey data which were obtained by a various agencies and private companies. Horizons such as acoustic basment and unconformity were interpreted using reflection seismic sections. Conrad discontinuity and Mohorovicic discontinuity were interpreted on refraction surveys and consulted previous study. Layer structure and velocity model were created on these horizons.
We obtain a result that understands geological structure in Nankai Trough. So in this session, we will take a discussion concerning structural characteristic based on the 3D velocity model.