HR: 1340h
AN: S33B-0321    [Abstracts]
TI: Vector Acoustic Sensors for Marine Seismic Surveys
AU: * Lindwall, D
EM: lindwall@nrlssc.navy.mil
AF: Naval Research Laboratory, Marine Geosciences Code 7432, Stennis Space Center, MS 39529 United States
AB: Using vector acoustic sensors for marine seismic and geo-acoustic surveys instead of the usual scalar hydrophones allows for acquiring a 3-D survey with the instrumentation and logistics similar to current 2-D surveys. Vector acoustic sensors measure the wave direction directly without the large and cumbersome arrays that hydrophones require. This concept was tested by a scaled experiment in an acoustic water tank that has a well controlled environment with a few targets. The experiment was scaled to the size of the available water tank and the frequency limits of the sensor. The sensor consists of a three-axis accelerometer as well as a hydrophone. The sound source was a standard hydrophone driven by a short 8 kHz pulse. The sensor was suspended in a fixed location and the hydrophone was moved about the tank by a robotic arm to insonify the tank from many locations. During part of the experiment, several floats (acoustic targets) were placed in the tank at diagonal ranges of approximately one meter. The accelerometer data show the direct source wave as well as the target scattered waves and reflections from the nearby water surface, tank bottom and sides. Vector data from single shots show that the wave motion direction can be readily determined for both direct waves and scattered waves. Without resorting to the usual methods of seismic imaging, which in this case would have only been two dimensional and relied entirely on the use of a synthetic source aperture, the three-dimensional volume of the tank environment was imaged. This work was supported by the Office of Naval Research, program element 61153N.
DE: 0994 Instruments and techniques
DE: 3094 Instruments and techniques
DE: 7294 Seismic instruments and networks (0935, 3025)
SC: Seismology [S]
MN: Fall Meeting 2005