摘要：

Passive hydrophone technologies and a variety of acoustic methods are applied in the deep-ocean and shallow water coastal environments of the northeast Pacific. Acatalog derived from U.S. Navy regional hydrophone array recordings of acoustic T- phases from seafloor earthquakes is examined, describing space/time patterns through empirical orthogonal function analysis of seismicity occurring along the spreading ridges and transform fault boundaries of the Juan de Fuca plate system from 1991-2002. A small, local array of ocean bottom hydrophones (OBH) deployed in 2006 at Axial Seamount on the Juan de Fuca ridge provides an acoustic record of building microseismicity preceding the most recent magmatic dike intrusion event in April 2011. Lastly, a year of acoustic recordings (2010-2011) from a seafloor hydrophone moored in the energetic, shallow coastal environment off the central coast of Oregon result in the first long-term, low frequency (10-840 Hz) ambient noise level measurements and baseline sound budget for the inner continental shelf waters of the northeast Pacific. The successful combination of passive acoustic techniques used in these studies displays a few of the advantages afforded by the efficient underwater transmission of acoustic energy in the marine environment.

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