Publication Date:
2022-05-26
Description:
The Ocean Bottom Seismometer Augmentation in the North Pacific Experiment (OBSANP,
June-July, 2013, R/V Melville) 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" (DSFA) 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). At least a subset of these arrivals correspond to bottomdiffracted
surface-reflected (BDSR) paths from an out-of-plane seamount. BDSR arrivals are
present throughout the water column, but at depths above the conjugate depth are obscured by
ambient noise and PE predicted arrivals. On the 2004 NPAL/LOAPEX experiment BDSR paths
yielded the largest amplitude seafloor arrivals for ranges from 500 to 3200km. The OBSANP
experiment tests the hypothesis that BDSR paths contribute to the arrival structure on the deep
seafloor even at short ranges (from near zero to 4-1/2CZ). The OBSANP cruise had three major
research goals: a) identification and analysis of DSFA and BDSR arrivals 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. On OBSANP we
deployed a 32 element VLA from 12 to 1000m above the seafloor, eight short-period OBSs and
four long-period OBSs and carried out a 15day transmission program using a J15-3 acoustic
source.
Description:
Funding was provided by the Office of Naval Research under contract #'s N00014-10-1-0987
and N00014-10-1-0510
Keywords:
Melville (Ship) Cruise MV1308
;
Underwater acoustics
;
Oceanographic instruments
Repository Name:
Woods Hole Open Access Server
Type:
Technical Report
Format:
application/pdf
Permalink
