HR: 1330h
AN: V32B-1016    [PDF]
TI: Hydroacoustic Records of the First Historical Eruption of Anatahan Volcano, Mariana Islands
AU: * Dziak, R
EM: robert.p.dziak@noaa.gov
AF: Oregon State University/NOAA, 2115 SE OSU Drive, Newport, OR 97365 United States
AU: Park, M
AF: Korea Ocean Research and Development Institute, P.O. Box 29, Ansan, 656-830 Korea, Republic of
AU: Matsumoto, H
AF: Oregon State University/NOAA, 2115 SE OSU Drive, Newport, OR 97365 United States
AU: Fox, C
AF: NOAA/Pacific Marine Environmental Laboratory, 2115 SE OSU Drive, Newport, OR 97365 United States
AU: Byun, S
AF: Korea Ocean Research and Development Institute, P.O. Box 29, Ansan, 656-830 Korea, Republic of
AU: Fowler, M
AF: Oregon State University/NOAA, 2115 SE OSU Drive, Newport, OR 97365 United States
AU: Haxel, J
AF: Oregon State University/NOAA, 2115 SE OSU Drive, Newport, OR 97365 United States
AU: Embley, R
AF: NOAA/Pacific Marine Environmental Laboratory, 2115 SE OSU Drive, Newport, OR 97365 United States
AB: For the past decade, NOAA/Pacific Marine Environmental Laboratory has monitored volcano-seismic activity from western Pacific island-arc volcanoes using an array of U.S. Navy hydrophones (called SOSUS) deployed at fixed locations throughout the North Pacific Ocean. SOSUS hydrophones are mounted within the SOFAR channel and record the hydroacoustic tertiary phase or T-wave of oceanic earthquakes from throughout the Pacific basin. Since acoustic T-waves obey cylindrical energy attenuation as opposed to the spherical attenuation of solid-earth seismic phases, sound channel hydrophones can detect often smaller and therefore more numerous earthquakes than land-based seismic networks. This property allowed for the detection of harmonic tremor from a submarine volcano in the Volcano Islands on hydrophones $>$14,000 km away in the eastern Pacific. The first historical eruption of Anatahan Volcano appears to have started (from satellite imagery) at 1730Z on 10 May, with an ash plume visible by 2232Z (BGVN, 5 May 2003). Records from a broadband seismometer deployed on nearby ($\sim$6.5 km) Sarigan Island indicate earthquake activity increased at about 1300Z on 10 May (D. Weins, pers com). SOSUS hydrophones in the western Pacific ($\sim$4000 km distant) also recorded increased earthquake activity at 1300Z on 10 May as well as continuous, low-frequency ($<$10 Hz) energy (possible volcanic tremor) that began about a day before the seismicity. The earthquakes and tremor were detected on only two SOSUS hydrophones and therefore it was not possible to estimate their source location. The arrival azimuth of the signals were, however, consistent with a source in the Mariana Islands. To complement the SOSUS hydrophone array coverage in the western Pacific Ocean, an array of five autonomous hydrophones were deployed in February 2003 (sponsored by NOAA's Ocean Exploration Program) within the SOFAR channel along the active island- and back-arc of the Mariana Islands. All five hydrophones (1-110 Hz bandpass) were deployed between $13\deg$N and $22\deg$N, with one hydrophone located within 50 km of Anatahan Island. These five hydrophone will be recovered in September 2003, and it is anticipated their data will provide insights into Anatahan, as well as Mariana Island wide, volcano-seismic activity.
DE: 7280 Volcano seismology (8419)
DE: 8414 Eruption mechanisms
DE: 8419 Eruption monitoring (7280)
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting