Tsunami warning system

The 8.4-magnitude earthquake off Sumatra on 12 September 2007 was felt in at least four countries, with tall buildings swaying as far as 2000 km away. It was followed by a series of powerful aftershocks, the strongest of which registered a magnitude of 6.6 and triggered a second tsunami alert for Indonesia, which was lifted about an hour later. The tsunami warning was issued at about 5:10pm Bangladesh time from Pacific Tsunami Warning Center (PTWC). The government of Bangladesh issued a tsunami alert referring to the Disaster Management Bureau (DMB), Ministry of Food and Disaster and asking people of the coastal belt to leave homes and rush for safer places since Tsunami might hit the coastal regions after midnight. Immediately after the warning, the deputy commissioners in the coastal districts and the Red Crescent Society made announcements through loudspeakers about the possible disaster and arranged for quick evacuation. Chittagong Port authorities alerted ships at berth and at the outer anchorage of a possible tsunami threat and kept their tugboats ready to face the situation. The Chittagong port and the City Corporation opened two control rooms to monitor the situation. The officer-in-charge of Swandip said about 70,000 people of the island took shelter in cyclone homes. Unconfirmed reports say that burglars looted valuables from some homes vacated by dwellers after the official tsunami alert.
The promptness of the action is highly appreciated but it is equally regrettable that a false alarm caused so much suffering to the people. Why those who issued Tsunami alarm for Bangladesh coast referring to the PTWC and other agencies failed to withdraw the same immediately after its withdrawal by the PTWC and the Indonesian Met Department? If it was done it could save people from enormous sufferings and financial loss.
What went wrong with Tsunami warning? The PTWC has been operational since 1949, originally as the Seismic Sea-wave Warning Center. It uses seismic data as its starting point, but then takes into account oceanographic data, mostly tide gauge data around the place of earthquake occurrence when calculating possible Tsunami threats. However, Tsunami was not a major concern prior to 2004 Sumatra Tsunami. Tsunami warning used to be treated as local concern, and no one was interested whether the issued warning was true or false. But after the 2004 Tsunami, the warning system got serious momentum with the same old method of calculating Tsunami threat like using seismic data and tide gauge data. As a result, Tsunami warning of March 28, 2005 Sumatra earthquake, July 17, 2006 Java earthquake, and lastly September 12, 2007 Sumatra earthquake all turned out to be false alarm.
Tsunami warning cannot be set simply by calculating magnitude and location of the seismic event and tide gauge data, neither it is so simple. There are more factors and conditions that need to be observed and interpreted for an effective warning of trans-oceanic Tsunami. Otherwise, the Tsunami warning in some cases will be ignored because people will not take it seriously.
Prof. Dr. Aftab Alam Khan,
Vice President, Bangladesh Earthquake Society (BES),
Department of Geology
University of Dhaka