HR: 1340h
AN: G53B-0884    [Abstracts]
TI: ENVISAT SAR and InSAR Observations of Deformation and Crater Floor Elevation Change of Anatahan Volcano, Mariana Islands
AU: * Wicks, C
EM: cwicks@usgs.gov
AF: USGS, 345 Middlefield Rd MS 977, Menlo Park, CA 94025 United States
AU: Yarai, H
EM: hyarai@usgs.gov
AF: USGS, 345 Middlefield Rd MS 977, Menlo Park, CA 94025 United States
AU: Lu, Z
EM: lu@usgs.gov
AF: SAIC, USGS/EROS, 47914 252nd Street, Sioux Falls, SD 57198 United States
AU: Helz, R
EM: rhelz@usgs.gov
AF: USGS, 12201 Sunrise Valley Drive MS 926A, Reston, VA 20192 United States
AB: Anatahan Volcano is a strato-volcano situated on a small 9 km by 3 km island in the Mariana Islands of the west Pacific Ocean. The volcano came to life with its first historical eruption in May 2003 ejecting a column of ash from the east crater up to 10 km into the atmosphere. The east crater is one of several craters that coalesce into a larger 5 km by 2 km caldera, the largest caldera in the volcanoes of the Mariana Islands. We will show results of a nascent InSAR study of Mariana volcanoes using European Space Agency (ESA) ENVISAT data. ESA began acquiring SAR data (IS2 and IS6 modes for both ascending and descending passes) over the Marianas Islands in November of 2004 at our request. Interferograms constructed from IS6 mode data display better coherence than those constructed from IS2 data. This coherence is reasonably well maintained from one acquisition to the next, and fairly well maintained over several months from Nov, 2004 to April, 2005. Limited explosive activity in late January and early February apparently did not destroy InSAR coherence through April 5. The largest of the eruptions, to date, occurred on April 5 (UT) about 12 hours after ESA acquired data over the island. Interferograms constructed using the April 5 image display a deformation field that is consistent with an inflating dike that trends SW from the east caldera to the south shore of the island. Since the April 5, 2005 eruption, there has been too much ash deposition and erosion to expect coherent interferograms for at least the near future. Because the inner walls of the east crater are steeper than the IS6 mode incident radar beams, which are incident about 40 degrees from vertical, we have used the change in radar shadow length to estimate the change in elevation of the crater floor. We found that the crater floor rose over 40 m between January 25 and March 1, 2005, and stayed at that level through the April 5 acquisition time. From this shadow length decrease, we have estimated a volume increase of about 27 million cubic meters. We will also extend the radar shadow tracking to post-eruptive SAR images as they become available.
DE: 1243 Space geodetic surveys
DE: 5480 Volcanism (6063, 8148, 8450)
DE: 8419 Volcano monitoring (7280)
DE: 8425 Effusive volcanism
SC: Geodesy [G]
MN: Fall Meeting 2005