On interseismic elevation changes observed near 75.5° E longitude in the NW Himalaya

Abstract

We interpret in this article the available observations of interseismic elevation changes along the Pathankot-Dalhousie leveling line near 75.5° E longitude in the NW Himalaya. We find the data consistent with the view that the major earthquakes of this section of the Himalayan convergent plate margin may occur in a manner similar to that inferred for subduction zones along the Pacific rim. In both cases, the main thrust zone (MTZ), a dipwise section of the plate boundary fault (PBF), which ruptures during major earthquakes, is locked in the interseismic period, and the overlying rocks experience downdip drag due to subduction of underlying rocks at the local plate convergence rate. We estimate that the MTZ may have a downdip width of only 25 km in the vicinity of the leveling line. We estimate also that, in the current interseismic period, enough strain may have accumulated already for the next major earthquake of the region.