An Experimental Multi-disciplinary observatory (VENUS) at the Ryukyu Trench using the Guam-Okinawa Geophysical Submarine Cable

J. Kasahara, R. Iwase, T. Nakatsuka, Y. Nagaya, Y. Shirasaki, K. Kawaguchi, J. Kojima


A multidisciplinary Ocean Bottom Observatory (MDOBO) was installed on VENUS (Versatile
Eco-monitoring Network by Undersea-cable System) a depth of 2,170 meters on the slope of the Ryukyu
Trench. In this context, Eco- refers to both economic (e.g., earthquake hazard mitigation) and
ecological motivation. The first step in this instillation was to insert a telemetry/power system into the
submarine coaxial cable; this system could then service the MODOBO, which consist of seven major
bottom sensor packages.
During August-September 1999, using a deep-towed unit and both manned and unmanned submersibles
coupled with precise ship navigation, the MDOBO system and its attendant cables were deployed over a
range of distances from 80 m to 1 km from the telemetry system, with several meter allowance for
navigational uncertainty in positioning. The unmanned submersible then extended the multi-conductor
extension cables from the instrument units toward the telemetry system and connected them to undersea
mateable connectors on a junction box installed on the submarine cable. The MDOBO collected one and
half months of continuous records. Several kinds of useful data were collected after installation, including
an aftershock (Ms=6.1) of the 1999 Chi-Chi earthquake (Ms=7.7) in Taiwan.


Decommissioned submarine cables;ocean bottom observatory;real-time telemetry;ecological monitoring,ecological monitoring;junction box;OBS

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X