HR: 0800h
AN: T31A-0495    [Abstracts]
TI: Increasing seismic activity at 9deg50'N on the East Pacific Rise RIDGE 2000 Integrated Studies Site from October 2003 through April 2004
AU: Weekly, R T
EM: rtweekly@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964-8000 United States
AU: * Tolstoy, M
EM: tolstoy@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964-8000 United States
AU: Waldhauser, F
EM: felixw@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964-8000 United States
AU: Bohnenstiehl, D R
EM: del@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964-8000 United States
AU: Kim, W
EM: wykim@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964-8000 United States
AB: Monitoring of micro-seismicity within the bull's-eye region of the R2K ISS at 9deg49'N - 9deg51'N on the East Pacific Rise has been ongoing since October 2003. Results from the first deployment (October 2003 - April 2004) will be presented with hypocenters determined using relative-relocation techniques. Analysis shows that there is a gradual and ongoing increase in the rate of activity over the 7 months of the deployment. Mean event rates increase from 31 events/day for the first quarter of the deployment period, to 55, 105, and 131 events per day for the 2nd, 3rd and 4th quarters, respectively. This gradual increase in activity suggests long-term changes in the magma body or changes in the hydrothermal cracking front. Preliminary analysis and event counts for the 2004-2005 deployment will be presented to assess whether or not the build up in activity seen in 2003-2004 continued. Numerous brief swarms are observed throughout the deployment and their locations will be studied relative to temporal changes in the vent temperature monitoring as well as variations in the fluid chemistry (see Von Damm et al., same session). Early analysis suggests two dominant areas of recurrent activity, between M-vent and Bio-9 and between Bio-9 and Tube-worm pillar. The exceptionally well-characterized and monitored seafloor at this site allows for unprecedented correlation of observed seismic activity with local biology, geology, geochemical and hydrothermal monitoring. As results from different monitoring activities continue to come in, a detailed understanding of the linkages should emerge.
DE: 3025 Marine seismics (0935, 7294)
DE: 3035 Midocean ridge processes
DE: 3050 Ocean observatories and experiments
SC: Tectonophysics [T]
MN: Fall Meeting 2005