Monday, July 26, 2010

One last look... then we drop 'em

To the left is a view of the combined ocean bottom seismometers and hydrophones (OBS) resting comfortably in the OBSIP shack on the deck of the R/V Marcus Langseth. OBSIP is the U.S. National Ocean Bottom Seismometer Instrument Pool. The particular instruments that we'll be using are from Wood's Hole Oceanographic Institution.

Each instrument is comprised of a short-period three-component geophone and a single hydrophone. As shown in the cartoon below (credit: WHOI), after the OBS hits the seafloor, the wire to the geophone burns over a few hours and the geophone drops to the seafloor at a distance from the main instrument housing to minimize noise. The hydrophone is positioned at the top of the plastic housing. Later, when it comes time to pick up the OBSs, we'll send a signal to each instrument to release from the bottom. Then they'll float to the water surface, and we'll pick them up.

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