Campbell Richard L.

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Campbell
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Richard L.
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  • Technical Report
    Ocean Bottom Seismometer Augmentation of the Philippine Sea Experiment (OBSAPS) cruise report
    (Woods Hole Oceanographic Institution, 2011-09) Stephen, Ralph A. ; Kemp, John N. ; McPeak, Sean P. ; Bolmer, S. Thompson ; Carey, Scott ; Aaron, Ernie ; Campbell, Richard L. ; Moskovitz, Brianne ; Calderwood, John ; Cohen, Ben ; Worcester, Peter F. ; Dzieciuch, Matthew A.
    The Ocean Bottom Seismometer Augmentation to the Philippine Sea Experiment (OBSAPS, April-May, 2011, R/V Revelle) addresses the coherence and depth dependence of deep-water ambient noise and signals. During the 2004 NPAL Experiment in the North Pacific Ocean, in addition to predicted ocean acoustic arrivals and deep shadow zone arrivals, we observed "deep seafloor arrivals" that were dominant on the seafloor Ocean Bottom Seismometer (OBS) (at about 5000m depth) but were absent or very weak on the Distributed Vertical Line Array (DVLA) (above 4250m depth). These "deep seafloor arrivals" (DSFA) are a new class of arrivals in ocean acoustics possibly associated with seafloor interface waves. The OBSAPS cruise had three major research goals: a) identification and analysis of DSFAs occurring at short (1/2CZ) ranges in the 50 to 400Hz band, b) analysis of deep sea ambient noise in the band 0.03 to 80Hz, and c) analysis of the frequency dependence of BR and SRBR paths as a function of frequency. On OBSAPS we deployed a fifteen element VLA from 12 to 852m above the seafloor, four short-period OBSs and two long-period OBSs and carried out an 11.5day transmission program using a J15-3 acoustic source.
  • Article
    Deep water towed array measurements at close range
    (Acoustical Society of America, 2013-10) Heaney, Kevin D. ; Campbell, Richard L. ; Murray, James J. ; Baggeroer, Arthur B. ; Scheer, Edward K. ; Stephen, Ralph A. ; D'Spain, Gerald L. ; Mercer, James A.
    During the North Pacific Acoustic Laboratory Philippine Sea 2009 experiment, towed array receptions were made from a towed source as the two ships transited from a separation of several Convergence Zones through a Closest Point of Approach at 3 km. A combination of narrowband tones and broadband pulses were transmitted covering the frequency band 79–535 Hz. The received energy arrives from two general paths—direct path and bottom bounce. Bearing-time records of the narrowband arrivals at times show a 35° spread in the angle of arrival of the bottom bounce energy. Doppler processing of the tones shows significant frequency spread of the bottom bounce energy. Two-dimensional modeling using measured bathymetry, a geoacoustic parameterization based upon the geological record, and measured sound-speed field was performed. Inclusion of the effects of seafloor roughness and surface waves shows that in-plane scattering from rough interfaces can explain much of the observed spread in the arrivals. Evidence of out-of-plane scattering does exist, however, at short ranges. The amount of out-of-plane scattering is best observed in the broadband impulse-beam response analysis, which in-plane surface roughness modeling cannot explain.