QUANTIFYING THE INTERACTION OF AN OCEAN BOTTOM SEISMOMETER WITH THE SEABED

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Authors
  1. Osler, J.C.
  2. Chapman, D.M.F.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN)
Abstract
A theory is presented for the coupling between an ocean bottom seismometer (OBS), the sediments upon which it rests, and the surrounding water. Assuming that rotational and tilt effects are negligible (or have been made negligible through instrument design), the response of the OBS to forced harmonic motion is considered that the measured ratio of velocities when the OBS is on the seabed and when it is freely suspended in water (for an identical force) completely characterizes the OBS/seabed interaction. This enables the velocity transfer functions to be directly calculated without recourse to a detailed model of sediment/structure interaction. An OBS was designed and constructed with good coupling to seabed motion and reduction of rocking effects as principal design criteria, including an onboard shaker to conduct in situ coupling experiments. The amplitude and phase of coupling data collected on a clay seabed provide transfer functions due to horizontal and vertical seabed motion and horizontal water motion. In addition, a simple mass-spring-dashpot model of OBS/seabed interaction permits the analysis of amplitude-only coupling data. TRUNCATED
Keywords
Geophones;Acoustic coupling;Seismoacoustic noise;Coupling transfer functions;Seabed motion;Sea floor vibrations
Date of publication
01 May 1998
Number of Pages
16
Reprinted from
Journal of Geophysical Research, vol 103, no B5, 1998, p 9879-9894
DSTKIM No
98-02330
CANDIS No
509233
Format(s):
Hardcopy;Document Image stored on Optical Disk

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