TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 50 (Nos. 11, 12), pp. 913-925, 1998

A new approach to geophysical real-time measurements on a deep-sea floor using decommissioned submarine cables

Junzo Kasahara1, Toshinori Sato1, Hiroyasu Momma2, and Yuichi Shirasaki3

1Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi-cho, Bunkyo-ku, Tokyo 113-0032, Japan
2JAMSTEC (Japan Marine Science and Technology Center), 2-15 Natsushima, Yokosuka, Kanagawa 237-0061, Japan
3KDD R & D Laboratories, 2-1-15 Ohara, Kamifukuoka-shi, Saitama 356-0003, Japan

(Received April 8, 1998; Revised October 16, 1998; Accepted October 17, 1998)

Abstract: In order to better understand earthquake generation, tectonics at plate boundaries, and better image the Earth's deep structures, real-time geophysical measurements in the ocean are required. We therefore attempted to use decommissioned submarine cables, TPC-1 and TPC-2. An OBS was successfully linked to the TPC-1 on the landward slope of the Izu-Bonin Trench in 1997. The OBS detected co-seismic and gradual changes during a Mw 6.1 earthquake just below the station at 80 km depth on November 11, 1997. A pressure sensor co-registered a change equivalent to 50 cm sea-level change. This suggests a high possibility detecting silent earthquakes or earthquake precursors if they exist.
A multi-disciplinary geophysical station has been developed for deep-sea floor using TPC-2 since 1995. The station comprises eight instrument sets: broadband seismometers, geodetic measurements, hydrophone array, deep-sea digital camera, CTD, etc.
These activities are examples that decommissioned submarine cables can be great global resources for real-time cost-effective geophysical measurements on a deep-sea floor.

Corresponding author E-mail: kasa2@eri.u-tokyo.ac.jp

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