HR: 1340h
AN: G43B-1192    [Abstracts]
TI: Ground deformation detected by precise leveling just above the estimated pressure source in Asama volcano
AU: * KIMATA, F
EM: kimata@seis.nagoya-u.ac.jp
AF: Nagoya University, Nagoya-shi, Aichi, Nagoya, 464-8602, Japan
AU: ISHIKAWA, K
EM: keita@seis.nagoya-u.ac.jp
AF: Nagoya University, Nagoya-shi, Aichi, Nagoya, 464-8602, Japan
AU: MATSUMURA, T
EM: t.matumura@met.kishou.go.jp
AF: Japan Meteorological Agency, Oiwake, Karuizawa, 389-0115, Japan
AB: Asama volcano Asama volcano erupted frequently in the first half of the 20th century, and almost stopped the eruption after then. However the volcano erupted in the top of volcano in September, 2004. Dike intrusion was estimated at the depth of 3km and 4km west from the Asama volcano from the ground deformation observed by GPS network around the volcano before and after the eruption (Murakami, 2005; Aoki et al., 2006). Precise leveling We started the precise leveling to the area just above the estimated dike intrusion from the mountain flank with a distance of 20 km in May, 2005 and repeated the leveling four times until May, 2007. Subsidence just above the estimated pressure source GPS measurements around the volcano shows the extension of the line lengths until July, 2005 and turn to the contraction after then. Leveling detected the uplift of 3mm on November, 2005, the subsidence on May, 2006, and the maximum subsidence of 10 mm just above the estimated dike intrusion on May 2007. Comparing the deformation with observed and calculated from source When we calculated the ground deformation by deflation of dike intrusion in semi-infinite elastic body using Okada model, it suggests the uplift just above the dike intrusion. As near field GPS network, established within 5 km from the summit after the eruption of September 2004 suggests a deflation of the volcano, one spherical deflation source is estimated in shallow area. Discussion of the refraction error of the precise leveling Refraction error of leveling is affected as an error of 30 mm in height measurements at the leveling route with the height deference of 800 m. The height deference of this leveling route is amounting to 1,000 m. As this leveling route is constructed in forest, refraction error is not so large.
DE: 1209 Tectonic deformation (6924)
DE: 8419 Volcano monitoring (7280)
DE: 8434 Magma migration and fragmentation
SC: Geodesy [G]
MN: 2007 Fall Meeting