India's tsunami warning system

Abstract

Tsunami is a system of ocean gravity waves formed as a result of large-scale disturbance of the sea floor that occurs in a relatively short duration of time. The Indian Ocean is likely to be affected by tsunamis generated mainly by earthquakes from the two potential source regions, the Andaman-Nicobar-Sumatra Island Arc and the Makran Subduction Zone. A state-of-the-art warning centre has been established at INCOIS with all the necessary computational and communication infrastructure that enables reception of real- time data from the network of national and international seismic stations, tide gauges and Bottom Pressure Recorders (BPRs). Earthquake parameters are computed in the less than 15 minutes of occurrence. A database of pre-run scenarios for travel times and run-up height has been created using Tunami N2 model. At the time of event, the closest scenario is picked from the database for generating advisories. Water level data enables confirmation or cancellation of a tsunami. Tsunami bulletins are then generated based on decision support rules and disseminated to the concerned authorities for action, following a standard operating procedure. The criteria for generation of advisories (warning/alert/watch) are based on the tsunamigenic potential of an earthquake, travel time (i.e. time taken by the tsunami wave to reach the particular coast) and likely inundation. The performance of the system was tested on September 12, 2007 earthquake of magnitude 8.4 off Java coast. The system performed as designed. It was possible to generate advisories in time for the administration and possible evacuation was avoided.