HR: 08:30h
AN: V31B-03    [PDF]
TI: Quasi-Periodic Episodes of Volcanic Tremor at Okmok Volcano, Alaska
AU: * Reyes, C G
EM: celso@giseis.alaska.edu
AF: Alaska Volcano Observatory, UAF Geophysical Institute 903 Koyukuk Drive P.O. Box 757320, Fairbanks, AK 99775 United States
AU: McNutt, S R
EM: steve@giseis.alaska.edu
AF: Alaska Volcano Observatory, UAF Geophysical Institute 903 Koyukuk Drive P.O. Box 757320, Fairbanks, AK 99775 United States
AB: A new seismic network, consisting of nine short-period stations, was installed at Okmok volcano, Alaska, in summer 2002. Continuous data began to be recorded in April 2003. Eventually, this array will be expanded to include four additional 3-component broadband stations and four co-located continuous GPS stations. The most recent eruption occurred in February - April 1997 and, like most historical eruptions, issued from Cone A - which is still steaming as of this writing. INSAR measurements of post eruptional deformation show that the volcano is inflating at a rate of $\sim$10 cm/yr (Mann and Freymueller, 2002). Seismically, there are very few local earthquakes; however, there has been nearly continuous low level tremor with stronger amplitude bursts occurring at a rate of about 2 per hour (2.2 $\pm$ 0.8). These bursts have durations generally in the range of 5-8 minutes. Most bursts begin abruptly, reach a maximum amplitude within 3 minutes, then decline gradually over the next several minutes. Many bursts resemble each other quite closely, suggesting that there is a single main process or source location. No systematic trends have yet been observed between duration and either amplitude or the length of the preceding interval. The tremor is composed of irregular waves with a broad range of frequencies between $\sim$1 and $\sim$20 Hz, with main peaks at $\sim$2.2 and $\sim$6.2 Hz, and with a lesser peak at $\sim$5.5 Hz. Okmok is the only volcano out of 25 monitored Aleutian volcanoes to display this type of tremor. This activity may be linked to magma transport and the observed high rate of deformation.
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