Publication Date:
2022-05-25
Description:
Author Posting. © Acoustical Society of America, 2013. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 134 (2013): 3307-3317, doi:10.1121/1.4818845.
Description:
Ocean bottom seismometer observations at 5000 m depth during the long-range ocean acoustic propagation experiment in the North Pacific in 2004 show robust, coherent, late arrivals that are not readily explained by ocean acoustic propagation models. These “deep seafloor” arrivals are the largest amplitude arrivals on the vertical particle velocity channel for ranges from 500 to 3200 km. The travel times for six (of 16 observed) deep seafloor arrivals correspond to the sea surface reflection of an out-of-plane diffraction from a seamount that protrudes to about 4100 m depth and is about 18 km from the receivers. This out-of-plane bottom-diffracted surface-reflected energy is observed on the deep vertical line array about 35 dB below the peak amplitude arrivals and was previously misinterpreted as in-plane bottom-reflected surface-reflected energy. The structure of these arrivals from 500 to 3200 km range is remarkably robust. The bottom-diffracted surface-reflected mechanism provides a means for acoustic signals and noise from distant sources to appear with significant strength on the deep seafloor.
Description:
The OBS/Hs used
in the LOAPEX field program were provided by Scripps
Institution of Oceanography under the U.S. National Ocean
Bottom Seismic Instrumentation Pool (SIO-OBSIP, http://
www.obsip.org). The OBS/H deployments themselves were
co-funded through direct funding to SIO-OBSIP by the
National Science Foundation and by Woods Hole
Oceanographic Institution under a grant from the WHOI
Deep Ocean Exploration Institute. The
LOAPEX source deployments and the moored DVLA receiver
deployments were funded by the Office of Naval
Research under Award Nos. N00014-03-1-0181 and
N00014-03-1-0182. The data reduction and analysis in this
paper were funded by the Office of Naval Research under
Award Nos. N00014-06-1-0222 and N00014-10-1-0510.
Additional post-cruise analysis support was provided to
RAS through the Edward W. and Betty J. Scripps Chair for
Excellence in Oceanography.
Keywords:
Acoustic arrays
;
Acoustic noise
;
Acoustic signal processing
;
Acoustic wave reflection
;
Acoustic wave velocity
;
Long-range order
;
Ocean waves
;
Seafloor phenomena
;
Seismometers
;
Surface acoustic waves
;
Surface energy
;
Underwater acoustic propagation
Repository Name:
Woods Hole Open Access Server
Type:
Article
Format:
application/pdf