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

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.

IIDAKA, H., T. DOI, T. SAITO, H. NAKKANO, S. SATO and Y. FUJINAWA (2000): Development of
maneuverable and flexible deep ocean observation by acoustic transmission, in ”Final report on the
VENUS project”, edited by J. KASAHARA, ERI, 47-56 (in Japanese with English abstract).
IWASE, R., K. KAWAGUCHI and K. MITSUZAWA (2000): Development of the multi-sensor
observation equipment, in ”Final report on the VENUS project”, edited by J. KASAHARA, ERI, 47-56
(in Japanese).
KASAHARA, J. (2000): (editor), Final report on the VENUS project, ERI, 206 pp. (in Japanese).
KASAHARA, J. (2002): Development of seismic real-time monitoring systems at subduction zones around
Japanese islands using decommissioned submarine cables, in “Science-Technology Synergy for Research
in the Marine Environment: Challenges for the XXI Century”, 47-57, Elsevier, Amsterdam.
KASAHARA, J., H. UTADA and H. KINOSHITA (1995): GeO-TOC project- Reuse of submarine cables
for seismic and geoelectric measurements, J. Phys. Earth, 43, 619-628.
KASAHARA, J., H. UTADA, T. SATO and H. KINOSHITA (1998a): Submarine cable OBS using a retired
submarine telecommunication cable: GeO-TOC program, Phys. Earth Planet. Intr., 108, 113-127.
KASAHARA, J., T. SATO, H MOMMA and Y. SHIRASAKI (1998b): A new approach to geophysical
real-time measurements on a deep-sea floor using decommissioned submarine cables, Earth Planets and
Space, 50, 913-925.
KASAHARA, J. and T. SATO (2000): Observation of the VENUS OBBS (Ocean Bottom Broadband
Seismometer), in ”Final report on the VENUS project”, edited by J. KASAHARA, ERI 127-133 (in
Japanese).
KASAHARA, J., Y. SHIRASAKI and H. MOMMA (2000): Multidisciplinary geophysical measurements on the ocean floor using decommissioned submarine cables: VENUS project, IEEE J. Ocean Engin., 25,
111-120.
KASAHARA, J., K. KAWAGUCHI, R. IWASE, Y. SHIRASAKI, J. KOJIMA and T. NAKATSUKA
(2001): Installation of the multi-disciplinary VENUS observatory at the Ryukyu Trench using
Guam-Okinawa geophysical submarine cable, (GOGC: former TPC-2 cable), JAMSTEC Deep Sea Res.,
18, 193-207.
KASAHARA, J., Y. SHURASAKI, K. ASAKAWA and K. KAWAGUCHI (2003): Scientific application
of AREANA network, in “Proc. The third international workshop on Scientific Use of submarine cables
and related technologies”, IEEE-03EX660, 272-275.
KATSUMATA, A., M. TAKAHASHI, S. ODAKA, Y. OBARA, H. ITO, M. OKADA, K. NAKAMURA
and M. NAKAMURA (2000): Study of the development of the tsunami observation system by use of
precise bottom pressure sensor, in ” Final report on the VENUS project”, edited by J. KASAHARA, ERI,
67-73 (in Japanese with English abstract).
KDD (1964): Special Issue on the Trans Pacific Cable-1, KDD Technical Jour., 42, 1-141, Tokyo (in
Japanese).
KDD (1976): Special Issue on the Trans Pacific Cable-2, KDD Technical Jour., 88, 3-75, Tokyo (in
Japanese).
KOJIMA, J., Y. KATO and Y. SHIRASAKI (2000): Development of the bottom telemetry system, in ”
Final report on the VENUS project”, edited by J. KASAHARA, ERI, 67-73 (in Japanese)
KOJIMA, J. (2003): Insulation measurement of undersea equipments and failure analysis of the
underwatrer connector on VENUS system, in “Proc. The third international workshop on Scientific Use
of submarine cables and related technologies”, IEEE-03EX660, 75-78.
MIKADA, H., K. HIRATA, H. MATSUMOTO, K. KAWAGUCHI, T. WATANABE, R. OTSUKA and S.
MORITA(2003): Scientific results from underwater earthquake monitoring using cabled observatories,
in “Proc. The third international workshop on Scientific Use of submarine cables and related
technologies”, IEEE-03EX660, 3-7.
NAGAYA, Y. (2000): Observation with seafloor-acoustic ranging system linked to submarine telecommunication cable, in ”Final report on the VENUS project”, edited by J. KASAHARA, ERI,
148-151 (in Japanese with English abstract).
NAGUMO, S. and D. A. WALKER (1989): Ocean bottom geoscience observation: Reuse of transoceanic
telecommunication cables, EOS Trans. AGU, 70, 673-677.
NAKATSUKA, T., T. MIYAZAKI, Y. MURAKAMI, Y. OGAWA and K. NISHIMURA (2000):
Development of deep-sea geomagnetic and electric field observation systems and its deployment at the
Okinawa site, in “Proc. The third international workshop on Scientific Use of submarine cables and
related technologies”, IEEE-03EX660, 25-30.
SHIRASAKI, Y., M. YOSHIDA, T. NISHIDA, K. KAWAGUCHI, H. MIKADA and K. ASAKAWA
(2003): ARENA: A versatile and multidisciplinary scientific submarine cable network of next generation,
in “Proc. The third international workshop on Scientific Use of submarine cables and related
technologies”, IEEE-03EX660, 226-231.
SUBMARINE CABLE ASSOCIATION (ed.) (2003): “Technologies of Japanese Submarine Cables”,
Published by Submarine Cable Association, Yokohama, 202 pp. (in Japanese).
WATANABE, K. (2000): Development of the hydrophone array, in ”Final report on the VENUS project”,
edited by J. KASAHARA, ERI, 17-21 (in Japanese).
WEBB, S. C. (1998): Broadband seismology and noise under the ocean, Rev. Geophys. Space Phys., 36,
105-142.