HR: 0800h
AN: U11B-0841    [Abstracts]
TI: Deformation Studies In Andaman and Nicobar Islands
AU: * Nagarajan, B
EM: gandrb@nde.vsnl.net.in
AF: Geodetic & Research Branch, Survey of India, Dehradun, 654428 India
AB: Geodetic & Research Branch of Survey of India being the National Mapping Organisation has the responsibility of providing precise horizontal and vertical control network for the country including connecting the various islands to the mainland. Precise GPS, High Precision Levelling and Tidal measurements are routinely taken up in the Andaman & Nicobar Islands, the last epoch from Great Sumatra earthquake being in April 2004. 32 days tidal observations also taken up in various habited islands to study sea level rise/fall to understand land subsidence/upheaval. Comparison of pre and post Tsunami vectors from Mainland to A & N Islands clearly show that the Islands have moved 2 to 3 meters in horizontal position towards the mainland and also the Islands have rotated in anti-clock wise directions. The GPS stations have moved in South Westerly direction with the magnitude varying from 2 to 3 meters in the Andaman Islands and up to 5 to 6 meters in the Great Nicobar Islands. It is also interesting to note that the GPS stations lying in the West coast of A & N Islands have shown greater movements than the stations like Long Islands, Govindgarh etc. lying in the Eastern coast. Thirty-two days tidal analysis was carried out using the tidal observations at Chatham Observatory, Portblair to ascertain the vertical movement. It is observed that there is a rise in local mean sea level of an order of 1.05 m. GPS observations taken just after Tsunami in early January,2005 also indicate the similar trend in the vertical movement. At most of the places it exhibits a subsidence of 0.52 m to 2.86 m except two places Ramakrishnapur and Govindgarh, where a rise of 0.51 m and 0.17 m was observed. This paper discusses the horizontal and vertical movements of the points at various epochs and the effects of the Great Sumatra Tsunami and its Socio economic impact in the region.
DE: 4564 Tsunamis and storm surges
DE: 7209 Earthquake dynamics (1242)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7299 General or miscellaneous
SC: Union [U]
MN: Fall Meeting 2005