Analysis of Deep Seafloor Arrivals observed on NPAL04

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2012-12Author
Stephen, Ralph A.
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Bolmer, S. Thompson
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Udovydchenkov, Ilya A.
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Dzieciuch, Matthew A.
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Worcester, Peter F.
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Andrew, Rex K.
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Mercer, James A.
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Colosi, John A.
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Howe, Bruce M.
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https://hdl.handle.net/1912/5736DOI
10.1575/1912/5736Keyword
Underwater acoustics; Ambient soundsAbstract
This report gives an overview of the analysis that was done on Deep Seafloor Arrivals since they
were initially presented in Stephen et al (2009). All of the NPAL04/LOAPEX (North Pacific
Acoustic Laboratory, 2004/ Long Range Ocean Acoustic Propagation Experiment) data on three
ocean bottom seismometers (OBSs) at ~5,000m depth and the deepest element of the deep
vertical line array (DVLA) at 4250m depth has been analyzed. A distinctive pattern of late
arrivals was observed on the three OBSs for transmissions from T500 to T2300. The delays of
these arrivals with respect to the parabolic equation predicted (PEP) path were the same for all
ranges from 500 to 2300km, indicating that the delay was introduced near the receivers. At
500km range the same arrival was observed throughout the water column on the DVLA. We
show that arrivals in this pattern converted from a PEP path to a bottom-diffracted surface
reflected (BDSR) path at an off-geodesic seamount.