Continuing a time series that commenced in 1991, the researchers will take advantage of a U.S. Navy hydrophone array (SOSUS) in the North Pacific to conduct a range of seismic/acoustic studies relevant to ridge crest processes. By analyzing T-phase data recorded at the hydrophones, the researchers will study seismic events on the Gorda, Juan de Fuca, and Explorer ridge systems, compile a catalog of small earthquakes in the circum-North Pacific region, link seismic events to tectonic/biological changes at the ridge crests, and monitor cetacean and anthropogenic noise in the deep ocean. A fundamental goal of the project is to provide the data on which to base rapid response cruises under the auspices of the RIDGE2000 time-critical studies program. The project will be coupled with both continuous monitoring and individual cruises that will measure vent chemistry and biological processes at the Juan de Fuca ridge crest, thus making possible potential links between the spatiotemporal distribution of seismic deformation and chemical and biological events. Broader impacts include service to the RIDGE2000 community, training of students, outreach through the build-a-hydrophone program, strengthened collaboration with U.S. government partners (U.S. Navy and NOAA), and continuation of a time series that may eventually prove important to observatory efforts.