HR: 08:30h
AN: U21C-02    [Abstracts]
TI: Crustal Deformations Associated With the Great Sumatra-Andaman Earthquake Deduced From Continuous GPS Observation
AU: * Hashimoto, M
EM: hasimoto@rcep.dpri.kyoto-u.ac.jp
AF: DPRI, Kyoto Univ., Gokasho, Uji, 611-0011 Japan
AU: Choosakul, N
EM: cnwatthn@geo.sc.chula.ac.th
AF: Chulalongkorn, Univ., Phayathai Road, Bangkok, 10330 Thailand
AU: Hashizume, M
EM: hashmich@geo.sc.chula.ac.th
AF: Chulalongkorn, Univ., Phayathai Road, Bangkok, 10330 Thailand
AU: Takemoto, S
EM: takemoto@kugi.kyoto-u.ac.jp
AF: Department of Geophysics, Kyoto Univ., Kitashirakawa Oiwakecho, Sakyo-ku, Kyoto, 606-8502 Japan
AU: Takiguchi, H
EM: taki@kugi.kyoto-u.ac.jp
AF: Department of Geophysics, Kyoto Univ., Kitashirakawa Oiwakecho, Sakyo-ku, Kyoto, 606-8502 Japan
AU: Fukuda, Y
EM: fukuda@kugi.kyoto-u.ac.jp
AF: Department of Geophysics, Kyoto Univ., Kitashirakawa Oiwakecho, Sakyo-ku, Kyoto, 606-8502 Japan
AU: Fujimori, K
EM: fujimori@kugi.kyoto-u.ac.jp
AF: Department of Geophysics, Kyoto Univ., Kitashirakawa Oiwakecho, Sakyo-ku, Kyoto, 606-8502 Japan
AB: We analyzed continuous GPS data from more than 20 sites in Asia, Australia and islands in Indian Ocean in order to detect crustal deformations associated with the Sumatra-Andaman earthquake of December 26, 2004. Coseismic steps can be recognized at sites about 3,000km away from the epicenter such as south China, the Philippines, and Diego Garcia Island in central Indian Ocean. The largest displacement of about 28cm is found at Phuket in Thailand about 600km away from the epicenter, about twice as large as that at Sampari, the nearest site in northern Sumatra. These observations suggest that larger slip than 13m occurred beneath the Nicobar Islands. Total moment is estimated to be 6.41x10²²Nm, equivalent to Mw9.14. Large postseismic displacements are observed at Phuket and Sampari during the first month after the mainshock, but the former is three times larger than the latter. This suggests that the spatial distribution of afterslip is different from the coseismic slip distribution. There was a change in rate in postseismic deformations at the end of January, 2005, which implies a possible mechanical relationship with swarm activity at that time in the Andaman Sea. We obtained different slip distributions from the postseismic displacements before and after the change in its rate. Slip was dominant on the segment south of the Nicobar Islands during January, but the distribution of afterslip became nearly uniform during February and March, 2005. The area where coseismic displacement from the Nias earthquake of March 28, 2005 is detected is much smaller than that from the December mainshock, but displacement at Sampari is larger than that during the mainshock. These displacements suggest about 4m slip on a shallow dipping thrust fault that gives 6.82x10²¹Nm (Mw8.49). Finally, total moment released by afterslip amounts to 3.12x10²²Nm which is equivalent to Mw 8.93 for about five months, including the afterslip for the Nias earthquake.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 8123 Dynamics: seismotectonics
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Union [U]
MN: Fall Meeting 2005