Exposure. A Newsletter for Ocean Technologists. Volume 8. Number 5.
Abstract
The Massachusetts Institute of Technology Seismology Laboratory has been building and deploying ocean bottom seismometer (OBS) systems for several years. We recently developed a free-fall system with an external geophone package. The geophone array, housed in a cylindrical pressure case, is deployed onto the ocean floor from the main instrument package after the main package settles on the bottom. The deployed geophone package (DGP) is attached to the end of a deployment arm and held against the body of the main OBS package during descent. After the main OBS package arrives on the bottom, the deployment arm releases, allowing the DGP to fall away from the main instrument and to settle some distance away (approx. 1 meter). After the DGP is settled into place, the deployment arm detaches itself from the DGP and retracts to its original position, allowing the DGP to be connected to the main OBS by only a connecting cable. A method was needed by which the deployment arm could be released and allowed to fall sometime after the whole instrument had been launched at the sea surface. Since the time of the actual release was not critical (between 2 and 8 hours after initial deployment), the release mechanism did not have to be particularly sophisticated. However, the device had to be extremely reliable; neither releasing too soon (before the instrument arrived on the bottom), nor too late (after the instrument had begun to record data). Also the link had to be strong enough to carry the combined weight of the DGP and the deployment arm, as well as the additional handling stresses associated with the launching from the deck of the ship. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1980
- Accession Number
- ADA092985
Entities
People
- Roderick S. Mesecar
Organizations
- Oregon State University