HR: 1330h
AN: V32B-1019    [PDF]
TI: Seismic recording of the Anatahan eruption
AU: * Pozgay, S H
EM: spozgay@seismo.wustl.edu
AF: Washington University, Dept. of Earth and Planetary Sciences, St. Louis, MO 63130 United States
AU: Wiens, D A
EM: doug@seismo.wustl.edu
AF: Washington University, Dept. of Earth and Planetary Sciences, St. Louis, MO 63130 United States
AU: Shore, P J
EM: patrick@seismo.wustl.edu
AF: Washington University, Dept. of Earth and Planetary Sciences, St. Louis, MO 63130 United States
AU: Sauter, A
EM: asauter@ucsd.edu
AF: Scripps Institute of Oceanography, 10550 North Torrey Pines Rd, La Jolla, CA 92037 United States
AU: Camacho, J T
EM: juantcamacho@hotmail.com
AF: CNMI Emergency Management Office, P.O. Box 10007, Saipan, MP 96950 United States
AB: The first historic eruption of Anatahan volcano was fortuitously recorded by a broadband PASSCAL seismograph installed on the island only 4 days prior to the eruption. Although covered by ash during the eruption, the seismograph continued to operate throughout the main two month period of activity on Anatahan. This seismograph, located about 6 km west of the active eastern crater, as well as a seismograph installed on Sarigan about 45 km to the north, provide a continuous record of activity during the eruption. We have manually analyzed and visually picked arrivals from the 14 day period beginning 4 days prior to the eruption, and we have implemented an automatic event identification algorithm for the rest of the eruption period that has been calibrated relative to the manually processed data. In addition, we have located many of the larger volcano tectonic (VT) earthquakes using the P and S wave arrivals at Anatahan and Sarigan as well as P wave polarization data. Although these locations are not highly accurate they serve to delineate the general spatial progression of the earthquake activity. No earthquakes occurred in the crater region during the 4 days prior to the eruption. The only significant precursory earthquake activity was a swarm of events on May 8 that were located about 15 km northeast of the island and significantly deeper than events directly associated with the eruption. The first VT event from Anatahan itself was recorded at about 02:00 hrs GMT on May 10. The number of events per hour increases dramatically between 02:00 and 07:00 GMT. A period of nearly continuous earthquake activity commences at about 06:20 GMT which corresponds well with the eruption time of 07:30 GMT estimated by the Volcanic Ash Advisory Center from satellite photos of the ash cloud. After about 36 hours of intense earthquake activity, the number of discrete earthquakes declined, and were replaced by nearly continuous volcanic tremor. Much of the later part of the eruption was characterized by continuous volcanic tremor, probably associated with the dome building period of activity.
DE: 1040 Isotopic composition/chemistry
DE: 3640 Igneous petrology
DE: 3655 Major element composition
DE: 7280 Volcano seismology (8419)
DE: 8419 Eruption monitoring (7280)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting