HR: 1340h
AN: B13A-0165    [Abstracts]
TI: Earthquake Monitoring at $9\deg$50'N on the East Pacific Rise RIDGE 2000 Integrated Studies Site
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: 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: In the fall of 2003 nine ocean bottom seismometers (OBSs) were deployed from the {\it R/V Keldysh} within the `bull's-eye' region of the R2K ISS at $9\deg$49'N - $9\deg$51'N on the East Pacific Rise as part of the Ridge 2000 Integrated Studies Site. These instruments were recovered using the {\it R/V Atlantis in April 2004}, and twelve more were deployed to take their place for a second year of monitoring (with three years total planned). During the turn-around cruise, two short temporary deployments (~4-8 days), of an additional 3 OBSs each, were accomplished to provide very dense instrument spacing (a few 100 m) around specific vents where {\it in situ} chemical monitoring was taking place (Luther et al.). Good data were collected on seven of the nine long deployment and six short deployment OBSs. We will present early results from analysis of these data including an estimate of the level of activity observed through-out the seven month period of the first deployment, and preliminary epicenters. Data will also be shown from the short temporary deployments. Early analysis of these data indicates an event rate of ~8 events per day for events where arrivals are apparent on at least three instruments, and may therefore expect to be located. Also notable in these data are pulses and prolonged periods of what appear to be tremor. This tremor is not generally coherent or synchronous from station to station and is therefore likely a very localized phenomena associated with hydrothermal fluid flow. The exceptionally well characterized and monitored seafloor at this site will allow for unprecedented correlation of observed seismic activity with local biology, geology, geochemical and hydrothermal monitoring. In addition, past and future detailed geophysical imaging of this area will provide an excellent context for observed faulting and fracturing.
DE: 3025 Marine seismics (0935)
DE: 3035 Midocean ridge processes
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting