HR: 1340h
AN: B13A-0180    [Abstracts]
TI: Local Earthquakes on the Endeavour Segment of the Juan de Fuca Ridge: First Seismic Results from the Keck Seismic/Hydrothermal Observatory
AU: * Wilcock, W S
EM: wilcock@ocean.washington.edu
AF: University of Washington, School of Oceanography Box 357940, Seattle, WA 98115 United States
AU: Barclay, A H
EM: andrew@ocean.washington.edu
AF: University of Washington, School of Oceanography Box 357940, Seattle, WA 98115 United States
AU: McGill, P R
EM: mcgill@mbari.org
AF: Monterey Bay Aquarium Research Institute, 7700 Sandholt Rd., Moss Landing, CA 95039 United States
AU: Stakes, D S
EM: debra@mbari.org
AF: Monterey Bay Aquarium Research Institute, 7700 Sandholt Rd., Moss Landing, CA 95039 United States
AU: Ramirez, T M
EM: tony@mbari.org
AF: Monterey Bay Aquarium Research Institute, 7700 Sandholt Rd., Moss Landing, CA 95039 United States
AU: Toomey, D R
EM: drt@newberry.uoregon.edu
AF: University of Oregon, Department of Geological Sciences, Eugene, OR 97403 United States
AU: Durant, D T
EM: troy@newberry.uoregon.edu
AF: University of Oregon, Department of Geological Sciences, Eugene, OR 97403 United States
AU: Hooft, E E
EM: emilie@newberry.uoregon.edu
AF: University of Oregon, Department of Geological Sciences, Eugene, OR 97403 United States
AU: Mulder, T L
EM: tmulder@nrcan.gc.ca
AF: Geological Survey of Canada, Pacific Geoscience Centre P.O. Box 6000, Sidney, BC V8L 4B2 Canada
AU: Ristau, J P
EM: jristau@nrcan.gc.ca
AF: Geological Survey of Canada, Pacific Geoscience Centre P.O. Box 6000, Sidney, BC V8L 4B2 Canada
AB: The W.M. Keck Foundation is supporting a five-year program to conduct prototype seafloor observatory experiments to monitor the relationships between episodic deformation, fluid venting and microbial productivity on the Endeavour segment of the Juan de Fuca Ridge and at the intersection of the Nootka fault and the Cascadia subduction zone. At the Endeavour, the experiment is sited near the central portion of the segment in a region where the spreading axis is characterized by a 100-m-deep, 500-m-wide axial valley that hosts five high-temperature hydrothermal vent fields spaced 2-3 km apart. The objectives of the experiment are to monitor local and regional seismicity around the vent fields in conjunction with the deployment of sensors and samplers to monitor temporal variations in the physical, chemical and ultimately microbial characteristics of the hydrothermal fluids. The Endeavour seismic network was installed in the summer of 2003 with the ROV ROPOS and comprises seven GEOSense three-component short-period corehole seismometers and one buried Guralp CMG-1T broadband seismometer. Five of the seven short-period seismometers were inserted in horizontal coreholes drilled into seafloor basalts; two were deployed in concrete monuments on the ridge flanks. It is the first seismic network on a mid-ocean ridge in which the sensors are deployed with an ROV beneath the seafloor in order to ensure good coupling and minimize the effects of current-generated noise. In August 2004, we used the ROV Tiburon to service the Endeavour seismic network and recover the first year of data. In addition, we installed a second broadband and three short period seismometers on the Nootka fault and a third broadband seismometer on the Explorer plate. The Endeavour seismic network performed well with all eight instruments recording high-quality data. A preliminary inspection of the data reveals many examples of local, regional and teleseismic earthquakes. One striking characteristic of the local earthquake records is the high fidelity of the shear wave records. The preliminary analysis of the local earthquake data will be performed as part of an undergraduate research apprenticeship class taught this fall at the University of Washington's Friday Harbor Laboratories.
DE: 7230 Seismicity and seismotectonics
DE: 7215 Earthquake parameters
DE: 3025 Marine seismics (0935)
DE: 3035 Midocean ridge processes
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting