HR: 0800h
AN: G51A-0066    [Abstracts]
TI: Surface deformation associated with the March 1996 earthquake swarm at Akutan Island, Alaska, revealed by C-band ERS and L-band JERS radar interferometry
AU: * Lu, Z
EM: lu@usgs.gov
AF: U.S. Geological Survey, EROS Data Center, SAIC, 47914 252nd Street, Sioux Falls, SD 57198 United States
AU: Wicks, C
EM: cwicks@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd. MS 977, Menlo Park, CA 94025 United States
AU: Kwoun, O
EM: okwoun@usgs.gov
AF: U.S. Geological Survey, EROS Data Center, SAIC, 47914 252nd Street, Sioux Falls, SD 57198 United States
AU: Power, J A
EM: jpower@usgs.gov
AF: U.S. Geological Survey, Alaska Volcano Observatory, 4200 University drive, Anchorage, AK 99508 United States
AU: Dzurisin, D
EM: dzurisin@usgs.gov
AF: U.S. Geological Survey, David A. Johnston Cascades Volcano Observatory, 1300 SE Cardinal Court, Building 10, Suite 100, Vancouver, WA 98683 United States
AB: Akutan volcano, situated in the west-central part of Akutan Island in the eastern Aleutian volcanic arc, is a composite stratovolcano with an active cinder cone inside a circular summit caldera about 2 km across. Akutan is one of the most active volcanoes in the Aleutian arc, producing more than 27 small to moderate explosions from the active intracaldera cone in the last two centuries. The most recent eruptive activity was a series of small steam and ash emissions between March and May 1992. In March 1996, an intense volcano-tectonic earthquake swarm beneath Akutan Island was accompanied by extensive ground cracking but no eruption of Akutan volcano. Radar interferograms produced from L-band JERS-1 and C-band ERS-1/2 images show uplift associated with the swarm by as much as 60 cm on the western part of the island. The JERS interferogram has greater coherence, especially in areas with loose surface material or thick vegetation. It also shows subsidence of similar magnitude on the eastern part of the island, and displacements along faults reactivated during the swarm. The axis of uplift and subsidence strikes about N70øW, which is roughly parallel to a zone of fresh cracks on the volcano's northwest flank, to normal faults that cut the island, and to the inferred maximum compressive stress direction. A common feature of models that fit the deformation is the emplacement of a shallow dike along this trend beneath the volcano's northwest flank. Both before and after the swarm, the northwest flank was uplifted 5-20 mm/year relative to the southwest flank, probably by magma intrusion. The zone of fresh cracks subsided about 20 mm during 1996-1997 and at lesser rates thereafter, possibly because of cooling and degassing of the intrusion.
DE: 8419 Eruption monitoring (7280)
DE: 8499 General or miscellaneous
DE: 6924 Interferometry
DE: 6969 Remote sensing
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting