Surface Deformation across Shillong Plateau and Bangladesh from GPS Data

Abstract:

Interseismic strain accumulation arising out of India-Asia plate convergence process was found to be more pronounced in the eastern-most segment of the Himalaya. The 1897 Assam earthquake (M 8.7) , one of the great Himalayan earthquakes within last 500 years, is believed to have occurred over the south dipping boundary fault of the Shillong plateau. All along the Himalayan belt except in the eastern segment under study, the Main Frontal Thrust or equivalents at the immediate foothill of the Himalaya marks the southern edge of the locked segment, and region of high rate of surface strain accumulation is confined within a arc-parallel strip of around 200 km width. In the last 200 km long easternmost segment of the Himalaya, the southern boundary of the convergence related surface shortening seems to have been extended further south, much beyond the Himalayan frontal thrusts. This unusually wider deformation zone includes entire Shillong plateau in north-eastern part of India and extends into Bangladesh. New data from a recently established 16 station GPS network stretched over Bhutan, India and Bangladesh, in association with earlier data from the Indian network in this region provide better insight into this complex tectonic problem.