Seismotectonics of the northeast Indian region based on GPS velocities, stress and strain rate field characterization

The North-Eastern (NE) area of India is bounded by the confluence of three major tectonic plates constituting two convergent plate boundaries that essentially govern the complex seismotectonic of this Himalayan region that renders it seismically most active.  The area studied in the present work is confined to the hyperactive zone contained in the grid 20^o - 30^o N latitude and 88^o -100^o E longitude.  We analyze five years of GPS data obtained from sixteen Global Positioning System (GPS) campaign mode stations and two permanent ones deployed in the NE region. These velocities are used in estimating dilatational and shear strain rates along with the principal axes of strains. The estimated dilatational strain rate ranges from -0.13 to 0.1 microstrain/yr. In general, the velocity and strain rate fields are consistent with ongoing India-Eurasia collision and Indo-Burma subduction processes. Superposed on this pattern, we find that the intense dilatational field corresponds to the vicinage of the region between the main boundary and central Himalayan thrusts (viz. MBT, MCT), and while it is moderate in some regions of Indo Burmese Arc (IBA). Three distinct regions with high compressive strain rate distribution are delineated along the thrust zones. Two of these regions corresponds to the regions where the Kopili fault and  Tista lineament transversely converge MCT and transgresses into the MBT/MCT in Sikkim Himalaya and Bhutan Himalaya respectively and other with northern syntax region,  posing a high seismic hazard. , Some pockets of moderate strain rate near to the intersection areas of Kopili, Dauki faults and IBA, positionally relate to the high seismic zones and are consistent well with the statistical seismology, seismic topography and potential field anomalies.  Our study focuses on velocity and strain rate distribution vis-à-vis seismicity and crustal heterogeneity in the region facilitating the estimation of earthquake hazard potential.