Chronology of major terrace forming events in the Andaman islands during the last 40 kyr

Abstract

Major earthquakes that trigger tsunamis are great natural hazards. The devastations caused by the December 26, 2004 Sumatran earthquake, and the March 11, 2011 Japan earthquake, and associated tsunamis will remain in our memories for a long time. Such events reaffirm the need for studying the cause and effects of large earthquakes of the past and to prepare the world better for the future. In such an effort, to understand the pattern of earthquakes and their effects on the geomorphic evolution, we have studied deformation history in the Andaman and Nicobar Islands, located in one of the most active convergent margins of the world. Focusing on tectonically formed coastal terraces and determining the timing of their formation from the exposed dead corals, we have been able to reconstruct the history of major earthquakes in these islands for the last 40 kyr. Our results in conjunction with the existing radiocarbon age data from coastal terraces of these islands appear to suggest that the frequency of major earthquakes (M > 7) in the region has increased during the last 9 kyr. In confirmation with some earlier work, we find evidences for a major earthquake and a tsunami between 500-600 cal yr BP and possibly 4 others during 6–9 cal kyr BP. Our results also indicate that there has been a continuous subsidence of the south Andaman Islands.