Inundation of sea water in Andaman and Nicobar Islands and parts ofTamil Nadu coast during 2004 Sumatra tsunami

摘要

The December 26, 2004 earthquake with a magnitude of M 9.0 off Sumatra, Indonesia, occurred at 6.29 am (IST) generated giant tsunami. Within few minutes after the earthquake, tsunami waves hit the Andaman and Nicobar group of islands. Data on seawater run-up levels recorded during tsunamis can help determining vulnerability lines for human safety. Field measurements made at selected locations in A & N islands have indicated the run-up levels varying from 1.5 to 5 m in Andaman Islands and 3 to 7 m in Nicobar Islands. In the case of Tamilnadu, it was between 2.8 and 3.9 m. Locations having gentle land slope values showed penetration of seawater to long distances compared to locations with fewer slopes. Penetration of seawater during the tsunami to long distances in Car Nicobar, Little Andaman and Nagapattinam revealed the vulnerability of low lying areas having gentle slope beaches/coastal land slopes to storm surges, tsunamis etc. Land subsidence has aggravated the problem of seawater inundation in A & N islands and the low lying areas adjoining the creeks face permanent problem of seawater inundation during high tides. Adoption of elevation based setback lines or vulnerability lines for human settlement planning along the coastal areas needs to be incorporated under relevant Acts.