HR: 1340h
AN: T33B-1375    [Abstracts]
TI: Regional hydroacoustic perspective of the January 2006 eruption at the East Pacific Rise, 9º- 50'N
AU: * Dziak, R P
EM: robert.dziak@oregonstate.edu
AF: Oregon State University/NOAA, 2115 SE OSU Drive Hatfield Marine Science Center, Newport, OR 97365, United States
AU: Bohnenstiehl, D R
EM: drbohnen@ncsu.edu
AF: North Carolina State University, Department of Marine, Earth and Atmospheric Sciences, Raleigh, NC 27695-8208, United States
AU: Matsumoto, H
EM: haru.matsumoto@oregonstate.edu
AF: Oregon State University/NOAA, 2115 SE OSU Drive Hatfield Marine Science Center, Newport, OR 97365, United States
AU: Fowler, M J
EM: matt.fowler@oregonstate.edu
AF: Oregon State University/NOAA, 2115 SE OSU Drive Hatfield Marine Science Center, Newport, OR 97365, United States
AU: Haxel, J H
EM: joe.haxel@oregonstate.edu
AF: Oregon State University/NOAA, 2115 SE OSU Drive Hatfield Marine Science Center, Newport, OR 97365, United States
AU: Lau, T
EM: andy.lau@noaa.gov
AF: Oregon State University/NOAA, 2115 SE OSU Drive Hatfield Marine Science Center, Newport, OR 97365, United States
AB: New information on the seismic activity from the January 2006 eruption at East Pacific Rise, 9°-50'N [Tolstoy et al., 2006; Cowen et al., 2007] was provided by the December 2006 recovery of OSU/NOAA autonomous hydrophones deployed along the EPR from 8°N-8°S and at 110°W and 95°W longitude. The hydrophones record the acoustic energy of seafloor earthquakes that propagate along the ocean sound channel with little attenuation over large distances. Frequency-magnitude relationships indicate the hydrophone catalogs are complete to body-wave magnitude 2.5 at the EPR. The hydrophones recorded data from December 2004 to 2006 and successfully recorded the seafloor spreading event and eruption that occurred on 22 January 2006. At this time the hydrophone data from 29 June 2005 through 30 January 2006 has been reviewed to compile an event count and locate earthquakes using their regional T- wave records. The hydrophones detected 255 earthquakes from the vicinity of 9°-50'N in the 3 weeks prior to 22 January (the inferred day of the eruption), then 252 events on 22 January, after which earthquake counts rapidly declined to background levels in less than 3 days. As Tolstoy et al (2006) observed, the peak seismic activity (and likely the diking event) occurred within 5 hours on 22 January, during which there is a two-hour period where events rates exceed 3 to 7 times the levels of other parts of the day. The vast majority of the detected events, however, were low magnitude and it was possible to locate only 20 earthquakes, 18 of which occurred during the 1 hour of peak earthquake activity on 22 January. These earthquakes are all located within a 35-km long area to the north and south of 9°-50'N, extending several kilometers past the section of ridge-crest where recent lava flows were observed. The earthquakes do not indicate migration occurred, although admittedly the dataset is limited in number. However the seismicity does take place in discrete time clusters, occurring in succession from being centered at 9°-50'N, south ~20 km to 9°-40'N, then back to back to as far north as 9°-59'N within the 1 hr time period. Roughly 15 hrs after the last earthquake located at the eruption site occurred a sequence of 17 earthquakes began along the western Clipperton Transform, and possibly on the eastern flank of the ridge segment to the north of 9°- 50'N, likely in response to the magma intrusion at the ridge crest. Tolstoy, M, et al., A seafloor spreading event captured by seismometers, Science, 1920-1922, 2006. Cowen, J.P., et al., Volcanic Eruptions at East Pacific Rise Near 9°-50′N, Eos, Trans. Amer. Geophys. Un., 88, No. 7, 81, 2007
DE: 7245 Mid-ocean ridges
DE: 8178 Tectonics and magmatism
DE: 8416 Mid-oceanic ridge processes (1032, 3614)
DE: 8419 Volcano monitoring (7280)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting