HR: 0800h
AN: V51C-1496    [Abstracts]
TI: Observations of Local Seismicity and Harmonic Tremor Using an Ocean Bottom Hydrophone Array at Brothers Volcano, South Kermadec Arc.
AU: * Haxel, J H
EM: joe.haxel@noaa.gov
AF: CIMRS/Oregon State University and NOAA/Pacific Marine Environmental Laboratory, 2115 SE OSU Drive Hatfield Marine Science Center, Newport, OR 97365
AU: Dziak, R P
EM: robert.p.dziak@noaa.gov
AF: CIMRS/Oregon State University and NOAA/Pacific Marine Environmental Laboratory, 2115 SE OSU Drive Hatfield Marine Science Center, Newport, OR 97365
AU: Lau, T K
EM: andy.lau@noaa.gov
AF: CIMRS/Oregon State University and NOAA/Pacific Marine Environmental Laboratory, 2115 SE OSU Drive Hatfield Marine Science Center, Newport, OR 97365
AU: Matsumoto, H
EM: haru.matsumoto@noaa.gov
AF: CIMRS/Oregon State University and NOAA/Pacific Marine Environmental Laboratory, 2115 SE OSU Drive Hatfield Marine Science Center, Newport, OR 97365
AB: The submarine Brothers volcano is an important link in the volcanic chain of the southern Kermadec Arc system in the Southwest Pacific Ocean north of New Zealand. The 3-3.5 km wide caldera has a center depth of 1850m and steep surrounding walls of 300-450m. Active hydrothermal venting distinguished Brothers as a point of focus for the New Zealand American Submarine Ring of Fire (NZASRoF) expeditions in 2004 and 2005. Due to its remote location, moderate to small magnitude seismicity around the Brothers area is largely unknown. In late September 2004, four ocean bottom hydrophones (OBHs) were deployed on the caldera floor. In April 2005, three of the four instruments were recovered intact. These three OBHs continuously recorded, for seven months, the low frequency (0-110Hz) acoustic field around Brothers volcano, in particular seismic P- and S-waves propagating through the crust and acoustic T-waves in the water column . Preliminary analysis reveals seismicity rates on the order of 106 earthquakes per month. In addition to seismic arrivals, low frequency harmonic tremor is frequently and independently observed on each of the OBH instruments, often occurring subsequent to the larger seismic events. Qualitative comparisons of these signals with tremor observed from the Volcano Islands south of Japan (Dziak and Fox, 2002) show them to be nearly equivalent in frequency structure, suggesting the origin of the tremor observed at Brothers may also be attributed to resonance of a magma-gas mixture in a large chamber or conduit near the water/ seafloor boundary.
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 4832 Hydrothermal systems (0450, 1034, 3017, 3616, 8135, 8424)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005