Bottom Interacting Acoustics in the North Pacific (NPAL13)
Abstract
To avoid confusion with other projects we are using a new acronym for this work - OBSANP (Ocean Bottom Seismometer Augmentation in the North Pacific). This project, OBSANP, addresses the coherence and depth dependence of deep-water ambient noise and signals. Seafloor signals are studied in the band from 50-400Hz and seafloor ambient noise is studied in the band from 0.03 - 80Hz. On NPAL04 we observed a new class of arrivals in long-range ocean acoustic propagation that we call Deep Seafloor Arrivals (DSFAs) because they are the dominant arrivals on ocean bottom seismometers (Mercer et al., 2009; Stephen et al., 2009; Stephen et al., 2008). We recently resolved that many of the DSFAs observed on NPAL04 are diffracted energy from a near-by seamount that is reflected from the sea surface (bottom-diffracted surface-reflected - BDSR - paths). This diffracted energy is a relatively weak signal on hydrophones on the DVLA, more than 750m above the seafloor, but it is by far the strongest signal on vertical geophones on the seafloor for signals out to 3200km range. One goal of OBSANP is to study these BDSR paths at shorter ranges and at more azimuths than were available from the 2004 experiment. This work is relevant to the Navy because it seeks to quantify and understand the signal propagation and noise floors that are necessary to evaluate and exploit seismo-acoustics for operational ASW systems.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 2012
- Accession Number
- ADA575117
Entities
People
- Peter F. Worcester
- Ralph Stephen
Organizations
- Woods Hole Oceanographic Institution