2003 and 2004 Upgrades and Additions to the Hawaii-2 Observatory
A.D. Chave, J.W. Bailey, S. Beaulieu, R. Butler, F.K. Duennebier, J.H. Filloux, D. Harris, M. Mandea, J.A. Orcutt, K. Smith, R. Stephen, P. Tarits, and F.L. Vernon
Abstract:
The Hawaii-2 Observatory (H2O) is a permanent deep ocean research facility located about halfway between California and Hawaii. The H2O infrastructure consists of a submarine cable termination and junction box which provides two-way digital data communications and power. At present, H2O instrumentation consists of a buried broadband seismic sensor. In 2003, a major upgrade to the H2O junction box is planned which will change the communications architecture to TCP/IP, making reconstruction of data streams on shore a system task. A new biological experiment, two seafloor geomagnetic observatories (SGO; one US and one French), and a Small Experiment Module (SEM) will also be installed. The goal of the biological experiment is determination of the short and long-term responses of benthic fauna to a temporally-variable food supply in a very food-limited environment. An instrument platform will include cameras to photograph the activities of animals near the seafloor and a sedimentation sensor to monitor the seafloor flux of particulates and phytoplankton pigments. The SGOs will each incorporate vector and scalar sensors for the relative geomagnetic field and its absolute magnitude, along with a gyrocompassbased method to measure the instantaneous absolute direction. In addition, the SGOs will measure the vector electric field, including removal of electrode drift. The SEM will be installed to supply a secondary interface to experiments. It will provide data interfaces and power for the H2O seismic system and up to eight additional low-data rate and low-power sensors. In 2004, a downhole seismic sensor will be installed in a borehole drilled about 1.5 km away from the H2O site and linked to the j-box using a fiber optic extension cable.
Ocean Crusta; Drilling at the Hawaii-2 Observatory
Stephen, R.A., Kasahara, J, Acton, G.D and the ODP Leg 200 Scientific Party
Abstract:
The primary goal of Ocean Drilling Project Leg 200 was to drill a suitable hole for a borehole seismometer at the long-term Hawaii-2 Observatory (H2O) site (see below). This was accomplished in Hole 1224D, where we installed a reentry cone and cemented casing 30 m into basaltic basement 1.48 km northeast of the H2O junction box. Above basement there was 28 m of soft, red clay. The cased basement interval, in which a borehole seismometer will be installed in 2004, consisted of massive basalt flows that had been cemented by calcite. This should provide good coupling for the seismometer to true earth motion. We also drilled a second single-bit hole, which was cored and logged, within 20 m of the first to a depth of 145 m into basement. The second hole was left with a free-fall funnel so that it also could be reentered using the wireline reentry technology to carry out other borehole experiments at the site. A suite of shipboard physical, well log, chemical and microbiological analyses that can be used to characterize the crust surrounding the observatory, was also carried out. The successful cultivation of oxidizing bacteria and the microscopic indication of further microbial structures within a cavity of basaltic rock confirm the presence and even activity of microbial life not only in deep marine sediments, but also in the Paleogene oceanic crust from the North Pacific. We tested a deep 3.5-kHz source that could be deployed on the VIT frame to inspect the shallow structure of the seafloor at a higher spatial resolution than conventional echo sounding. Measurements of ship noise during the drilling operations were also acquired on the shallow buried seismometer at the Hawaii-2 Observatory.
The Hawaii-2 submarine cable system is a retired AT&T telephone cable system between San Luis Obispo, California, and Makaha, on Oahu, Hawaii. The cable system was originally laid in 1964. In 1998 investigators from Incorporated Research Institutions for Seismology (IRIS), the University of Hawaii and Woods Hole Oceanographic Institution installed a long-term seafloor observatory about halfway along the cable (~140°W, 28°N). The junction box has eight underwater make-break connections. About 500 W of power is available from the junction box, and there is ample capacity for two-way, real-time communications with seafloor instruments. Data channels from the seafloor can be monitored continuously via the Oahu end of the cable to any lab in the world.
SN-1: the first node of the Italian seafloor observatory network - background and perspective
Paolo Favali, SN-1 Team and NEMO Collaboration
Abstract:
On October 9th, 2002, the seafloor observatory SN-1 (Submarine Network -1) was successfully deployed in 2105 m w.d. offshore Catania (Sicily Island, Ionian Sea) and at 16:15 of the same day started operation. The area is close to the seismogenic structure responsible of major earthquakes occurred in the area.
The project, funded by the Italian National Group for the Protection against Earthquake (GNDT), is coordinated by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) and has a partnership including Universities, Research Institutes, and the industrial company Tecnomare (ENI group).
SN-1 was straightforward derived from the previous GEOSTAR observatory, funded by the European Commission in the period 1995-2001, which performed a deep-sea mission of 7 months in 2000-2001 at about 2000 m w.d. in the southern Tyrrhenian Sea.
SN-1 observatory will be connected to a submarine cable owned and deployed by the Italian National Institute for Nuclear Physics (INFN), having the main purpose to carry out a scientific experiment of natural neutrino detection in deep sea (NEMO Project). Some power and fibre optic lines of this cable will be made available to SN-1 through a suitable underwater junction box. In this way SN-1, that is presently powered by batteries, will receive power from shore and will be able to communicate in real time with a shore station. This will make possible the complete integration of SN-1 to the existing Italian land-based network, and significantly contribute to the knowledge of a key sector of the central Mediterranean geodynamics.
The presentation will be devoted to the description, the goals and the preliminary results of SN-1 project. An overview will be also given of the results of GEOSTAR deep-sea mission and on the third phase of GEOSTAR (ORION-GEOSTAR 3) which purpose is the set-up of a underwater monitoring network including a main node (GEOSTAR prototype) and 2 nodes in acoustic linked.
Scientific results from underwater earthquake monitoring using cabled observatories
Hitoshi Mikada, Kenji Hirata, Hiroyuki Matsumoto, Katsuyoshi Kawaguchi, Tomoki Watanabe, Riyo Otsuka, Shigehiko Morita
Abstract:
Scientific results started appearing in the literature using realtime and continuous time series of data obtained on the seafloor for seismic and micro-tsunamic observations. JAMSTEC has developed three out of a total of eight cabled observatories in the Japanese water. The installed observatories are all operating to aid earthquake studies for disaster mitigation at the future potential hazards which take place at plate boundaries surrounding the Japanese islands. Along with earthquake activity monitoring purposes, it has become clear that there are potentially and scientifically meaningful outcome from such observations. We summarize the latest scientific results from monitored data produced by our cabled observatories and, then, to demonstrate advantages of such underwater seismic and tsunamic stations. Until now, three main areas could be pointed out as meaningful scientific products from cabled observations: (1) fine mapping of offshore seismicity, (2) modeling of micro-tsunamic pressure fluctuations caused by deep earthquakes, and (3) constraining earthquake source parameters such as source depths of offshore events using tsunami simulation. They are all interesting scientific results from the observational data but could also readily be exploited for earthquake studies on deformation processes at the plate boundaries and on early tsunami warning system as a part of future disaster mitigation methdologies. It is obvious that newly deployed monitoring systems have revealed, at least partially, meaningful phenomena which have been invisible due to lack of observations in the offshore. Technical and theoretical developments for offshore earthquake minitoring must be well considered for profound perception of geophysical processes associated with offshore seismic activities
AOS :The Adaptable Observation System for Real-time Seafloor Observation (P)
Katsuyoshi KAWAGUCHI, Hitoshi Mikada, Hiroko Sugioka and Hiroyuki Matsumoto
Abstract:
The submarine cable connected earthquake monitoring system is one tool for observation and had been deployed typical seismogenic zones around the Japan since 1970s. Although, high efficiency seismic observation requires a high-density seismic measurement network, there is considerable technological difficulty in deploying as many sensors on the seafloor as on land. The existing observation network is still small scale and insufficient for an ideal observation network covering Japan. To solve this problem, JAMSTEC developed an expandable and replaceable satellite measurement station called the Adaptable Observation System (AOS) and designed the newest cable system to extend the existing cable observation using this system. The AOS is a battery operated mobile observatory connected to the backbone cable system by the thin fiber cable to ensure real-time data recovery. The system consists of a branching system, a junction box, a fiber cable, and a battery system for 6-month operation. The branching system is a part of backbone cable system and the other equipment make up the observation site. Installation and construction of the AOS will be conducted by a towed vehicle and an ROV. Submarine thin fiber cable is too delicate to install to the seafloor from the sea surface as same manners as backbone submarine cable. It is necessary to use some device to lay the cable right above the seafloor. The thin fiber cable laying system was designed to store more than 10km of thin fiber cable in a cable bobbin and to maintain the tensile strength in the cable laying operation. Installation and construction of the AOS were conducted at the Off-Kushiro-Tokachi area by the underwater vehicles in JAMSTEC. The first trial of this system were successfully operated and confirmed the efficiency of mobile observatory in the 6 month observation. We believe this kind of system is a powerful too for future real-time seafloor observation and provides a chance to extend existing seafloor networks from in line to a wider area.
Multi-disciplinary VENUS observation at the Ryukyu Trench using Guam-Okinawa Geophysical Submarine Cable (P)
Junzo Kasahara, Ryoichi Iwase, Tadashi Nakatuka ,Koji Nagaya, Yuichi Shirasaki, Katsuyoshi Kawaguchi and Jun'ichi Kojima
Abstract:
A multi-disciplinary VENUS (Versatile Eco-monitoring Network by Undersea-cable System) observatory, which equips seven geophysical instrument groups, was installed at the depth of 2,170 meters on the slope of the Ryukyu Trench. Prior to the installation of the VENUS multi-disciplinary ocean bottom (MDOBO) observatory, an ocean-bottom telemetry system, which has functions to supply electrical power to the MDOBO, and the submarine coaxial cable were installed at ocean bottom. The installation of the multi-disciplinary ocean bottom observatory was done by use of deep-towing unit and ROV Kaiko-10K. During the period of August- September 1999, seven instrument groups of MDOBO were deployed at the target position, at 80-1000 meter distances from the telemetry system, with several meters allowances using a deep-towing unit. To install the instrument at the exact location, the mother ship of deep-towing unit was precisely navigated. The extension cables were also dropped from the deep-towing unit. The ROV Kaiko-10K extended multi-conductor extension cables from instrument units towards the ocean-bottom telemetry system and connected them to undersea mateable connectors on the junction box. The MDOBO collected one and half month records. Some useful data were observed since the installation.
Off Hatsushima Island observatory in Sagami Bay : Multidisciplinary long term observation at cold seepage site with underwater mateable connectors for future use (P)
Ryoichi Iwase, Kenichi Asakawa, Hitoshi Mikada, Tadanori Goto, Kyohiko Mitsuzawa, Katsuyoshi Kawaguchi, Kenji Hirata, Yuka Kaiho
Abstract:
Off Hatsushima Island observatory was primarily developed and installed by JAMSTEC (Japan Marine Science and Technology Center) in 1993, on the seafloor at a depth of 1175 m southeast off Hatsushima Island in Sagami Bay, Central Japan, which is one of the most significant cold seepage sites. The observatory was equipped with two video cameras, a CTD sensor, a current meter, an sub-bottom thermometer with two probes, a seismometer and a hydrophone for the purpose of real time long term multidisciplinary monitoring of deep seafloor environment at chemo-synthetic biological communities with cold seepage. The observatory revealed geophysical and biological events occurred on the seafloor, such as the mudflows and sedimentation generated by swarm earthquakes whose epicenters were located about 7 km southwest of the observatory, spawning of clams triggered by water temperature change, and so on.
The observatory including submarine cable was rebuilt comprehending new technologies such as underwater mateable connectors (optical / electrical) developed after the deployment of the primary observatory and replaced in March, 2000. The connectors were assigned for four serial ports with DC power supply retained for additional sensors, one pair of auxiliary power supplying line and four auxiliary fiber optic lines. One of two video cameras of the present observatory is a Super HARP (High-gain Avalanche Rushing Photoconductor) camera, which is far more sensitive than a CCD camera. The observatory is also equipped with a transmissometer, an ADCP (Acoustic Doppler Current Profiler), a tsunami pressure gauge (a precise pressure gauge) and a gamma ray spectrometer in addition to the same sensors as those of the primary observatory. Unfortunately, however, the current meter broke just after the deployment, and the observatory was deployed at another clam colony about 40 m north of the previous observatory where the cold seepage seemed to be less active.
In order to repair the current meter and to make some adjustment on the other sensors, the observatory was recovered in March, 2002. It was redeployed in November, 2002 at almost the same position where the primary observatory had been located. Higher heat flow than that of the previous location has been observed and gray bacteria mats were recognized at the present site. As a next step, the observatory is planned to be utilized as a test bed, such as the field tests of newly developed magnetometer and gravity meter by connecting them to the underwater mateable connectors.