HR: 0800h
AN: G51A-0047    [Abstracts]
TI: Geodetic constraints for the mechanism of Anatahan eruption of May 2003
AU: * Watanabe, T
EM: glposys@cc.kochi-u.ac.jp
AF: Faculty of Science, Kochi University, Akebono-cho 2-5-1, Kochi, 780-8520 Japan
AU: Tabei, T
EM: tabei@cc.kochi-u.ac.jp
AF: Faculty of Science, Kochi University, Akebono-cho 2-5-1, Kochi, 780-8520 Japan
AU: Matsushima, T
EM: mat@sevo.kyushu-u.ac.jp
AF: Institute of Seismology and Volcanology, Kyushu University, 2-5643-29 Shin'yama, Shimabara, Nagasaki, 855-0843 Japan
AU: Kato, T
EM: teru@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, The University of Tokyo, Yayoi 1-1-1, Bukyo-ku, Tokyo, 113-0032 Japan
AU: Nakada, S
EM: nakada@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, The University of Tokyo, Yayoi 1-1-1, Bukyo-ku, Tokyo, 113-0032 Japan
AU: Yoshimoto, M
EM: myoshi@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, The University of Tokyo, Yayoi 1-1-1, Bukyo-ku, Tokyo, 113-0032 Japan
AU: Chong, R
EM: rcchongemo@hotmail.com
AF: Emergency Management Office, P.O. Box 501704 CK, Saipan, 96950 Northern Mariana Islands
AU: Camacho, J T
EM: jtcamacho@cnmiemo.gov.mp
AF: Emergency Management Office, P.O. Box 501704 CK, Saipan, 96950 Northern Mariana Islands
AB: Anatahan Island is located at the southern end of the Mariana volcanic chain. On May 10, 2003 the first eruption occurred in its history and the eruptive activity continued to June 2003. Although volcanic activity declined in the second half of 2003, it resumed in April 2004. In order to determine crustal deformation associated with the eruption, we conducted GPS measurement on July 2003 at a benchmark (ANAT) located about 7km west-northwest of the active crater, where GPS campaign measurements had been repeated since 1992. In the period from January to July 2003 covering the eruption, a significant subsidence as large as 21cm was detected but horizontal movement was much smaller. At the same site, we started continuous GPS measurement on July 2003 to monitor transient deformation in terms of magma migration. On January 2004, we established another permanent GPS site (ANA2) at the northeastern part of the island about 3km far from the active crater to better constrain spatial pattern of the deformation. Coordinates time series at ANAT show a change of trend at around the beginning of 2004. Another subsidence of 2.9cm and a westward motion of 2.2cm were detected in the period from July to December 2003, and in turn an uplift of 5.3cm and an eastward motion of 0.8cm in the period from January to June 2004. We model three inflation/deflation sources for three different time periods, which are aligned straight and deepened westward at a dip-angle of 30 degrees from the active crater. Although the present model is very preliminary and non-unique, geodetic data will give adequate constraints on modeling the eruption mechanism.
DE: 1749 Volcanology, geochemistry, and petrology
DE: 1208 Crustal movements--intraplate (8110)
DE: 1645 Solid Earth
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting