HR: 17:30h
AN: S24A-07    [Abstracts]
TI: Systematic Search for Background Seismicity Rate Changes and Correlations at Alaskan Volcanoes
AU: * Kore, K R
EM: krkore@giseis.alaska.edu
AF: Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775 United States
AU: McNutt, S R
EM: steve@giseis.alaska.edu
AF: Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775 United States
AU: Christensen, D H
EM: doug@giseis.alaska.edu
AF: Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775 United States
AB: Recent studies have noted a correlation between large earthquakes and localized seismicity rate changes, particularly those associated with volcanic systems. In this study, we analyzed the Alaska Volcano Observatory (AVO) seismicity catalog from late 1989 through mid-2004 for patterns of background seismicity rate changes at the individual monitored volcanoes throughout the Aleutian Arc. We expand the recent studies to include seismic swarms and background seismicity rate changes as well as volcanic eruptions and regional earthquakes. We assume that seismicity rate changes reflect a change in stress on either a local scale, or perhaps over a regional scale when correlated over several volcanoes. The primary analysis was to identify seismicity rate changes at the individual volcanoes. Once all of the rate changes were identified using a z-test, they were examined to determine whether they were man-made or natural. The man-made rate changes were excluded from further study. Of the 27 volcanic regions monitored by AVO, 10 had background seismicity rate changes. Each of these regions had a different characteristic seismicity rate, which can change as often as three times per year or as seldom as once every ten years. Of particular interest are time periods when several volcanic regions have simultaneous rate changes or other significant activity including eruptions, swarms, rate changes at neighboring volcanoes, and large regional earthquakes from the Aleutian subduction zone. For example, in 1996, seven different volcanic regions experienced significant activities: seismic swarms at Akutan (March), Iliamna (August), Strandline Lake (September), and in the Katmai region (October), a deformation episode began at Mt. Peulik (October), an eruption at Pavlof (September), and a background seismicity rate change at Spurr (October). In 1998, Strandline Lake and Spurr experienced a seismicity rate change in early April, and Redoubt had a rate change in early May. The latter rate changes are coincident with the onset of a slow deformation event in the subduction zone of the Cook Inlet region, as determined by GPS data. Other coincident events were noted in the studied regions, but these are still under study.
DE: 7280 Volcano seismology (8419)
DE: 7299 General or miscellaneous
DE: 7200 SEISMOLOGY
SC: Seismology [S]
MN: 2004 AGU Fall Meeting