Tsunami waves recorded at Kirinda and Colombo on March 28: NARA

Tide gauges operated by the National Aquatic Resources Research and Development Agency (NARA) at Kirinda and Colombo have measured tsunami waves resulting from the March 28 Sumatra earthquake.

A maximum wave height of 2.3 m was measured at Kirinda while at Colombo (Mutwal Fishery Boat Harbour) the maximum wave height was 0.5 m, NARA said in a release.

The waves were due to an earthquake measuring 8.7 on the Richter scale at 10.09.36 pm (Sri Lanka time) to the north of the Island of Nias.

The waves were recorded at both locations, approximately three hours after the earthquake. The first tsunami waves arrived at 0105 hours at Kirinda while at Colombo they were recorded 10 minutes later.

Dr. E. M. S. Wijeratne from NARA said the tsunami waves were smaller than those recorded during the December 26 tsunami.

On Boxing day a maximum tsunami wave height of 2.3 m was recorded by the NARA tide gauge in Mutwal harbour. "This time only a 0.5 m wave was recorded," Dr. Wijeratne said. "Compared to the normal tidal range of 0.6m, the observed water levels due to tsunami waves were very significant".

Prof. Charitha Pattiaratchi from the University of Western Australia said this is the third recorded instance within the past 122 years that tsunami waves have been recorded in Sri Lanka - the others being the Krakatoa volcanic eruption in 1883 and the December 26 tsunami. He added: "The effects of the March 28 earthquake on Sri Lanka was much smaller because the tsunami waves were directed away (to the south) from Sri Lanka and also the region affected by the earthquake was much smaller (200 km for the March 28 earthquake vs 1,200 km for the Boxing day earthquake).

Receding water levels were also observed at many coastal regions of Sri Lanka. Commander Y. N. Jayaratne of the Sri Lanka Navy said Naval observers, stationed at coastal regions after the tsunami warning was issued, reported receding of water levels from 0100 hours for about 15-20 minutes and has been significant in places like Tangalle (seven) m and Trincomalee (five) m, but surprisingly no observations in Batticaloa.

The Naval teams also observed notable differences from Pulmudai to Muttur and again from Kirinda to Galle, but all were very minor when compared to the previous devastating tsunami.

Khalid