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 ∼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

Rupture model of Mw 7.8 2015 Gorkha, Nepal earthquake: constraints from GPS measurements of coseismic offsets

We estimate coseismic offsets at 20 sites in India due to the 25 April 2015 Gorkha, Nepal (Mw 7.8) earthquake. Only four sites in the Indian region, immediately to the south of the rupture, showed discernible coseismic horizontal offsets ranging between 3 and 7 mm toward north. We invert these offsets along with 13 other offsets at GPS sites in Nepal and 33 offsets at sites in China, for the estimation of slip distribution on the causative rupture. We assume that rupture occurred on the Main Himalayan Thrust (MHT). In our estimated slip model, high slip reaching ∼5 m occurred east of the mainshock epicenter, and the slip on rupture terminated close to the Main Boundary Thrust (MBT). Thus the rupture for this earthquake remained blind, increasing the potential for future earthquake in the shallow, updip unruptured part of the MHT