HR: 0800h
AN: U11B-0838    [Abstracts]
TI: Postseismic Deformation in the Central Andaman Islands
AU: * Puchakayala, J P
EM: jpuchkyl@memphis.edu
AF: Center for Earthquake Research Information, 3876 Central Ave, Memphis, TN 38152 United States
AU: Smalley, R
EM: rsmalley@memphis.edu
AF: Center for Earthquake Research Information, 3876 Central Ave, Memphis, TN 38152 United States
AU: Bilham, R
EM: Roger.Bilham@colorado.edu
AF: University of Colorado at Boulder, Department of Geological Sciences, 2200 Colorado Avenue, Boulder, CO 80309 United States
AU: Lowry, A
EM: arlowry@abdu.colorado.edu
AF: University of Colorado at Boulder, Department of Geological Sciences, 2200 Colorado Avenue, Boulder, CO 80309 United States
AU: Batacharjee, A
EM: anjan_bhat@yahoo.co.in
AF: University of Tezpur, Tezpur University, Napaan, Tezpur, AS 784028 India
AB: The December 26, 2004 Sumatra-Andaman earthquake generated horizontal displacements at Port Blair totaling 3.08 m and vertical subsidence of 0.6-0.9m, indicating 1.6 m arc normal and 6.2±0.6 m dextral coseismic slip on the plate interface. Displacements occurred steadily beginning 10 minutes after the mainshock and were largely complete within 30 minutes after the mainshock. Although continuous GPS measurements were not initiated until 24 days after the mainshock by us and other groups, it is possible from these records to inferthat postseismic deformation in this interval did not exceed 10% of the coseismic displacements. Postseismic deformation continues at present at an exponentially decaying rate. Between January and June 2005, Port Blair has moved 4.5 cm south, 15 cm west and 10 cm up, suggesting postseismic slip downdip of the coseismic rupture and/or viscoelastic relaxation of the mantle. Elastic models of the region based on GPS coseismic slip observations provided by Center for Earth Science Studies (CESS) are consistent with reports of uplift from the islands: North Sentinel (50 km west of Port Blair) rose by 1.0±0.2 m, Port Blair and Middle Andaman subsided by about 1 m and Havelock Island (32 km east) showed no significant vertical deformation. We report data from five campaign sites in the Andaman Islands measured thrice since the earthquake that permit viscoelastic and afterslip models of postseismic deformation to be developed and assessed.
DE: 3010 Gravity and isostasy (1218, 1222)
DE: 4804 Benthic processes, benthos (0408)
DE: 7209 Earthquake dynamics (1242)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Union [U]
MN: Fall Meeting 2005