Henri O. Berteaux

The seafloor borehole array seismic system (SEABASS) and VLF ambient noise

The Seafloor Borehole Array Seismic System (SEABASS) has been developed to measure the pressure and threedimensional particle velocity of the VLF sound field (2–50 Hz) below the seafloor in the deep ocean. The system consists of four three-component borehole seismometers (with an optional hydrophone). a borehole digitizing unit, and a seafloor control and recording package. The system can be deployed using a wireline re-entry capability from a conventional research vessel in Deep Sea Drilling Project (DSDP) and Ocean Drilling Project (ODP) boreholes. Data from below the seafloor are acquired either onboard the research vessel via coaxial tether or remotely on the seafloor in a self-contained package. If necessary the data module from the seafloor package can be released independently and recovered on the surface. This paper describes the engineering specifications of SEABASS, the tests that were carried out, and preliminary results from an actual deep sea deployment. VLF ambient noise levels beneath the seafloor acquired on the Low Frequency Acoustic-Seismic Experiment (LFASE) are within 20 dB of levels from previous seafloor borehole seismic experiments and from land borehole measurements. The ambient noise observed on LFASE decreases by up to 12 dB in the upper 100 m of the seafloor in a sedimentary environment.

Deep sea moorings fishbite handbook

Prepared for the Office of Naval Research under contract No. N00014-84-C-0134, N R 083-400.

Surface Telemetry Engineering Mooring (STEM)

A mooring has been developed to collect and transmit oceanographic and meteorological data via satellite links. Data telemetered included currents (from 50 to 250 m), water and air temperature, wind, relative humidity, barometric pressure, and various engineering parameters. The unique aspect of the STEM design was the use of electromechanical cable for both the strength member of the mooring and the electrical connection between the subsurface instruments and the surface buoy. The surface mooring was deployed 150 m south of Cape Cod in 2700 m of water in November 1987 and retrieved in May 1988. It operated successfully through the harsh North Atlantic winter.<<ETX>>

Self Deployable Deep Sea Moorings

Funding was provided by the Office of Naval Technology under Contract No. N00014-90-C-0098.

Seafloor borehole array seismic system (SEABASS)

This work was carried out under JHU Contract # 602809-0 and under ONR contracts #N00014-89-C-0018, #N00014-89-J-1012, and #N00014-90-C-0098.

Bottom array specifications for the low frequency acoustic seismic experiment (LFASE)

Report prepared under Office of Naval Research Contracts #N00014-89-C-0018, N00014-89-J-1012 and Office of Naval Technology Contract #00014-90-C-0098, WHOI Project #13/1012

Testing and evaluation of SURLYN foam and SPECTRA fiber ropes for buoy systems applications

Funding was provided by the Office of Naval Research through contract Number N00014-84-C-0134.

The Deep Sea Moorings Fishbite Problem

Evidence gathered to date clearly shows that moorings set far away from continental shores are subjected to severe fishbites. These bites occur from the surface to depths well within the bathypelagic zone, 1000 meters or more. The dimension of the fishbite problem is first reviewed. A data base which spans over twenty years and encompasses hundreds of moorings deployed world wide is used to delineate the space and time dependence of fishhbite attacks. This information is important when evaluating risks. Who are the culprits and why they do it is reviewed next. This knowledge is important when devising preventative methods. Granted that fishbite damage is a real possibility, how does one distinguish it from other plausible causes of rope failure? Observations, laboratory procedures, and rationales used to answer this question with a fair degree of assurance are described next. Finally the paper reviews the preventive and the curative methods which hopefully can protect mooring lines from the mechanical damage inflicted by fish teeth.

In Situ Measurements of the Dynamics of A Full Scale Bottom Moored Mine Model

Funding was provided by the Naval Surface Warfare Center under Contract No. N60921-91-C-0216.

Integrated seawater sampler and data acquisition system prototype : final report

Abstract : This report documents the work performed by the Woods Hole oceanographic Institution (WHOI) and the Battelle Memorial Institute from August 1988 to December 1992 in the NSF sponsored development of an Integrated Seawater sampler and Data Acquisition Prototype. After a 6-month initial design study, a prototype underwater profiling unit was designed and constructed, containing the water acquisition subsystem, CTD and altimeter, control circuitry and batteries. A standard WHOI CTD was adapted for use in the underwater unit and was interfaced to the underwater controller which had a telemetry module connecting it with a dock control unit. This enabled CTD data to be logged in normal fashion on shipboard while additional commands and diagnostics were sent over the telemetry link to command the underwater units water sampling process and receive diagnostic information on system performance. The water sampling subsystem consisted of 36 trays, each containing a plastic sample bag, the pump and control circuitry. The sample bags, initially sealed in a chemically clean environment, were opened by pumping the water out of the tray, thus forcing water into the bag by ambient pressure. The command system could select any bag, and control the water sampling process from the surface with diagnostic information on system altitude, depth, orientation and cable tension displayed in real time for operator information. At sea tests confirmed the operation of the electrical and control system. Problems were encountered with the bags and seals which were partially solved by further post cruise efforts. However, the bag closing mechanics requires further development, and numerous small system impovements identified during the cruises need to be implemented to produce an operational water sampler. Finally, initial design for a water sampler handling and storage unit and water extraction system were developed but not implemented.