Bottom interaction in long range acoustic propagation


DOEI Project Funded: 2004

Project Summary

What are the primary questions you are trying to address with this research?
We are trying to understand long range acoustic propagation in the ocean in the frequency band from 1 to 100Hz.

What is the significance of this research for others working in this field of inquiry and for the broader scientific community?
We have a number of anecdotal observations that long range propagation in this band is not adequately explained by traditional SOFAR channel propagation. Our goals are: 1) to understand the interplay between oceanographic mode coupling (internal waves, etc), bathymetric mode coupling (abyssal hills, sea mounts, mid-ocean ridges, etc), and bottom attenuation, and 2) to observe the vertical structure of T-phases and the seabed response to controlled sources for validation against forward models.

What is the significance of this research for society?
Underwater sound in this frequency band is used to study a broad range of processes including marine mammal activity and marine seismology (earthquakes under the ocean). In order to make progress in these disciplines we need to understand the acoustic propagation process.

When and where will this investigation be conducted?

This project will make seafloor seismic observations in the North Pacific from September 2004 to July 2005.

What are the key tools or instruments needed to conduct this research?
Ocean Bottom Seismometers

What are the greatest challenges - physical or intellectual - to conducting this investigation?
Our seafloor observation systems push the limits of available low-power computer technology. We also use advanced mathematics to quantitatively predict long range acoustic propagation for comparison with observations.

Is this research part of a larger project or program?
Not yet. We are using this opportunity to provide material for a proposal for a larger program.