HR: 1400h
AN: S23A-11    [Abstracts]
TI: Advanced ocean floor network for earthquakes and tsunamis around the Nankai Trough in southwestern Japan
AU: * Kaneda, Y
AF: Marine Technology Center, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
AU: Kawaguchi, K
AF: Marine Technology Center, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
AU: Araki, E
AF: Marine Technology Center, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
AU: Matsumoto, H
AF: Marine Technology Center, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
AU: Nakamura, T
AF: Marine Technology Center, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
AU: Kamiya, S
AF: Marine Technology Center, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
AU: Hori, T
AF: Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 3173-25 Syowa-cho Kanazawa-ku, Yokohama, 236-0001, Japan
AU: Baba, T
AF: Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 3173-25 Syowa-cho Kanazawa-ku, Yokohama, 236-0001, Japan
AB: The Nankai Trough is well known as the mega thrust earthquake with an interval of 100-150years. In this area, there are three seismogenic zones such as the Nankai, Tonankai and Tokai seismogenic zone. Therefore, in many researches focusing on the mega-thrust earthquakes around the Nankai trough, the structural researches using refractions and reflections seismic has succeeded to image the key structures to understand recurrences of mega thrust earthquakes around the Nankai Trough. Moreover, results of earthquake recurrence cycle simulation show that the first ruptures seems to occurred around the Tonankai earthquake rupture zone in each recurrence cycle, and the clear segment boundary between the Tonankai and Nankai earthquake rupture zones off the Kii peninsula was analyzed using tsunami data. The 1944 Tonankai and the 1946 Nankai earthquakes, each hypocenter was located off the Kii peninsula. So, the imaged irregular structures such as a key structure at the segment boundary between the Tonankai and Nankai earthquake rupture zone seems to act as the controller of the Tonankai-Nankai mega-thrust earthquake recurrence system. By the advanced simulation study of recurrence cycles of mega-thrust earthquakes around the Nankai Trough, these irregular structures seem to act as a controller of recurrence cycle and pattern of mega- thrust earthquakes in the Nankai Trough. Based on these researches, we proposed and have been starting to deploy the dense ocean floor observatory network system equipped with multi-kinds of sensors such as seismometers, pressure gauges etc., focusing on the understanding of crustal activities off Kii peninsula including the Tonankai/Nankai earthquake rupture zones. The new project of MEXT as the kind of Japanese government is starting from FY2006. This observatory system a will be the one of most advanced scientific tools to understand the mega thrust earthquakes around the Nankai trough. This advanced dense ocean floor observatory network system has useful functions and purposes as follows, 1) Redundancy, Extension and advanced maintenance system using the looped cable system, junction boxes and the ROV/AUV etc. 2) Speedy evaluation and notification for earthquakes and tsunamis Especially, the evaluation and notification for tsunami will be improved remarkably using dense ocean floor observatories. 3) Provide observed data such as ocean floor deformation derived from pressure gauges to improve the simulation and modeling researches about the mega-thrust earthquakes 4) Understanding of the interaction between the crust and upper mantle around subduction zone. In this paper, we will explain the advanced dense ocean floor observatory network system in detail and emphasize the purpose and importance of this system.
DE: 0545 Modeling (4255)
DE: 4262 Ocean observing systems
DE: 4294 Instruments and techniques
SC: Seismology [S]
MN: 2007 Joint Assembly