Abstract

The nature of instrumentally recorded seismicity for a part of the Burma-Andaman-Nicobar arc bounded by latitudes 2° and 24°N and longitudes 91° and 99°E was investigated. Based on the spatial distribution of the earthquakes and their focal mechanism solutions, four tectonic units were identified. From the south going northward, these are the Sumatra trench region, characterized by strike-slip and thrust faulting, the Andaman spreading ridge, characterized by normal and a few strike-slip faults, the Andaman-Nicobar ranges, where faulting is mostly thrust type, and the Indo-Burman ranges region, dominated by thrust faulting. The stress orientations in these segments and their changes with depth were studied in relation to the tectonics of the region. The direction of maximum compression in the Burma-Andaman-Nicobar region is NE-SW to N-S, compatible with the postulated motion of the Indian plate. Changes in stress orientations are attributable to local tectonics.

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