Acoustic lance: New in situ seafloor velocity profiles
نویسندگان
چکیده
The acoustic lance is an instrument developed to obtain in situ compressional wave velocity and attenuation ~Q! profiles for a sedimentary layer of several meters thickness at the sediment– seawater interface. The self-contained instrument consists of ten independent recording channels with a linear array of receivers embedded in the seafloor below a broadband acoustic source. It provides in situ recording of full waveforms to determine interval velocity and attenuation. The system can be attached to a gravity corer or to a specially designed probe. A comprehensive experiment was carried out in Mid-Atlantic Ridge sediment ponds where the lance made in situ measurements, and core samples were recovered. Core data agree well with in situ data in one location, but disagree in other locations. Lance data indicate that the sediment ponds have similar in situ velocity distributions, with an acoustic channel much thinner than that predicted by earlier investigators. © 1996 Acoustical Society of America.
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