Seismicity in Andaman - Nicobar - Java - Sumatra Region and its Bearing on the Volcanism in the Region, With Special Reference to the Barren Island.

Barren Island volcano in the Andaman Sea (Indian Ocean) is the lone active volcano in the Indian Subcontinent. The island showed renewed activity (commenced from May 28, 2005) after the great earthquake of Sumatra (December 26, 2004) along with increased mud volcanism in Bartang (south of Barren Island) and first ever reported mud volcanism on Narcondum (north of Barren Island) in the Andaman-Nicobar Archipelago. These islands lie on a volcanic arc that extends from the extinct volcanoes like Mt. Popa, Mt. Wuntho of Myanmar in the north to the active volcanoes of Sumatra and Java in the south. Regional tectonism of this region is largely driven by the subduction of the Indo-Australian plate beneath the Asian (Burmese) plate. Regional seismicity pattern reflects different tectonic regimes, namely, thrust dominated subduction front, strike-slip faulting (west Andaman fault) and the extensional processes in the Andaman spreading center. Earthquakes of magnitude more than 4.5 on Richter Scale are quite frequent in the region and are related to the subduction-related processes. Continuous seismic activities in the Andaman-Nicobar-Java-Sumatra region cannot be dealt with separately as evident from the increased volcanic activities following the great earthquake of Sumatra. More recently increased seismic activity in the vicinity of the dormant volcano of Mt. Toba is very much likely to culminate in a catastrophic eruption of this volcano in near future.