HR: 0800h
AN: G51A-0057    [Abstracts]
TI: Deformation of the Aniakchak Caldera, Alaska, Mapped by InSAR
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: 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: Neal, C
EM: tneal@usgs.gov
AF: U.S. Geological Survey, Alaska Volcano Observatory, 4200 University Dr., Anchorage, AK 99508 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
AB: Aniakchak Volcano, Alaska, a stratovolcano with a summit caldera about 10 km in diameter, is located 670 km southwest of Anchorage on the Alaska Peninsula. The caldera was formed by collapse about 3,500 years ago during an eruption of more than 50 km\^3 of andesite-dacite pyroclastic debris. Eruptions since the caldera-forming event have produced numerous vents and cones. Aniakchak's most recent eruption occurred in 1931 from a crater located near the base of the west caldera wall. We investigate the deformation of Aniakchak Caldera using 19 ERS-1/2 interferometric synthetic aperture radar (InSAR) images acquired from 1992 through 2002. InSAR images through this time period reveal that the 10-km-wide caldera has been subsiding. The pattern of subsidence does not reflect the distribution of pyroclastic deposits from the last eruption of the caldera in 1931. The maximum subsidence is identified near the center of the caldera, with a rate of as much as 13 mm/yr. Deformation outside the caldera is insignificant. Least-squares inversion of the multi-temporal deformation maps indicates that the subsidence rate has been relatively constant over the time of investigation. Modeling the deformation with a Mogi point source locates the source of subsidence at about 4 km beneath the caldera center, which is consistent with past reports on the depths of magma storage based on geochemical analysis. In addition, recent field surveys observed CO2 coming out of a lake inside the caldera and identified several fumaroles within the caldera. These observations suggest that the causes of the subsidence are probably due to cooling or degassing of magma body, and/or reduction of the pore fluid pressure of a cooling hydrothermal system.
DE: 8499 General or miscellaneous
DE: 6924 Interferometry
DE: 6969 Remote sensing
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting