Global Positioning System (GPS) Measurements of Crustal Deformation across the Frontal Eastern Himalayan Syntaxis and Seismic-Hazard Assessment

Tectonics and earthquake occurrence processes of the two Himalayan syntaxes are complex. Their limited accessibility has restricted seismological investigations in these regions, resulting in poor knowledge about the geodynamic processes. Here, we provide Global Positioning System (GPS) measurements of crustal deformation across the frontal eastern Himalayan syntaxis (EHS). In this region, the Indian plate obliquely underthrusts the Eurasian plate, and the eastward-extruding Tibetan plateau moves around the EHS due to India-Eurasia convergence. Our GPS measurements in the region suggest that the frontal EHS accommodates at least similar to 20 mm/yr of oblique convergence between the Indian and Eurasian plates. Under the frontal EHS, on which this convergence is accommodated through a stick-and-slip process, the 65 km wide main thrust zone of the plate boundary interface currently is locked. These measurements and the limited information about the great 1950 Assam earthquake (M-w 8.6) suggest that this great earthquake probably occurred in the EHS.