Earth Planets Space, Vol. 58 (No. 2), pp. 211-215, 2006
B. Nagarajan1, I. Suresh2, D. Sundar2, R. Sharma1, A.K.Lal1, S. Neetu2, S. S. C. Shenoi2, S. R. Shetye2, and D. Shankar2
1Geodetic and Research Branch, Survey of India, 17, E. C. Road, P. B. 77, Dehra Dun, Uttaranchal 248001, India
2National Institute of Oceanography, Dona Paula, Goa 403004, India
(Received June 30, 2005; Revised October 26, 2005; Accepted October 26, 2005; Online published February 17, 2006)
The Great Tsunami of 26 December 2004 is described using data from seven tide gauges in India and others from surrounding areas in the Indian Ocean. The tsunami struck the Indian east coast around 0330 UTC. The amplitude was 2 m above the tide at Chennai, Paradip, and Colombo. The east coast of India (and of Sri Lanka) was hit shortly after high tide; Tuticorin and Colombo, however, were hit shortly after low tide. The tsunami wave propagated northward along the Indian west coast. All these gauges are to the west of the earthquake zone and the detided sea levels show first a rise in sea level with the arrival of the tsunami, and then a sharp decrease. Spectral and wavelet analysis of the detided series show that the maximum amplitude was at a period of 35-45 minutes, with another maximum around 20 minutes. Along the Indian east coast, however, there is another broad peak between 1-2 hours within the first few hours after the first tsunami wave.
Key words: Earthquake, tsunami, Sumatra, Andaman, tide gauge, wavelet.