HR: 0800h
AN: T31B-0504    [Abstracts]
TI: Time-Critical Studies: Rapid response to Transient Dynamic Mid-Ocean Ridge Events
AU: Dziak, R P
EM: robert.p.dziak@noaa.gov
AF: Oregon State University/NOAA, 2115 SE OSU Drive HMSC/OERD, Newport, OR 97365 United States
AU: * Cowen, J P
EM: jcowen@soest.hawaii.edu
AF: University of Hawai'i, Department of Oceanography 1000 Pope Rd, Honolulu, HI 96822 United States
AU: Baker, E T
EM: edward.baker@noaa.gov
AF: NOAA/Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115-634 United States
AU: Bohnenstiehl, D R
EM: del@ldeo.columbia.edu
AF: Lamont Doherty Earth Observatory, P.O. Box 1000 61 Route 9W, Palisades, NY 10964-1000 United States
AB: The Time-Critical Studies (TCS) Theme of Ridge 2000 focuses on observations of the immediate geochemical and geobiological consequences of magmatic and tectonic events along the global mid-ocean ridge system. NOAA's T-Phase Monitoring Program has accessed the U.S. Navy's NE SOSUS data in real-time since 1993, providing the TCS community with detection of seismicity associated with eruptive or tectonic activity along the Juan de Fuca (JFR) and Gorda Ridges. This remote detection of earthquake swarms, coupled to NSF and NOAA funding for pre-event staging of equipment and supplies, allows directed and increasingly well-organized field responses to event sites. On 27 February 2005, one of the largest submarine earthquake sequences recorded with SOSUS occurred at the Endeavour segment of the JFR. The swarm met all criteria for magmatic earthquake sequences (see Dziak et al. poster and upcoming EOS article). This swarm differed from other plume-producing swarms in that it migrated more slowly (< 0.1 m/s) and over less distance (< 30 km) and occurred entirely within an overlap zone rather than within the bathymetric minimum of a segment. Despite the ambiguous character of the earthquake swarm, the Event Response Community responded since: (1) Although the swarm appeared to be magmatic, there is no way to confirm seafloor or water-column effects without in situ observations; and (2) absent a seafloor eruption, the physical process of injecting magma into the crust should cause significant faulting and fissuring that could result in the release of hydrothermal fluids. The high intensity of the earthquake swarm greatly increased this possibility. This response effort marked the sixth time since 1993 that a research cruise was organized for rapid response to the site of earthquake activity. The response team was on station just 6 days after notification of the seismic swarm, the fastest response yet mounted. Although the team detected no evidence of a new lava flow, or event-related hydrothermal discharge, the thoroughness and alacrity of the response demonstrates the vitality of the program and the dedication of the scientists and funding agencies involved.
DE: 7280 Volcano seismology (8419)
DE: 8416 Mid-oceanic ridge processes (1032, 3614)
DE: 8424 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8135)
DE: 8434 Magma migration and fragmentation
SC: Tectonophysics [T]
MN: Fall Meeting 2005