Geomorphic Mapping Reveals ~NW-SE Extension in NW Himalaya

Abstract

The work presented here shows new mapping of an array of ~NE-SW trending normal faults in NW Himalaya. This is achieved by geomorphic mapping of tectonic landforms using a variety of freely available satellite images that include Google maps, global earth, and global multi-resolution topography. The geomorphic mapping is performed by tracing of active fault ruptures, faulted glacial landforms, fault scarps, topographic breaks, deflected drainages, triangular facets, ridge axes offset, and broken Holocene to Recent sedimentary deposits. The results show that the faults are dominantly trending ~NE-SW with a few ~NNW-SSE. The faulting is widespread and extends for >140 km. These faults suggest ~NW-SE extension on a regional scale, and the tectonic transport is—orthogonal to the regional convergence between India and Southern Tibet. The faults are active and the entire region is undergoing regional ~NW-SE extension, and therefore, a new tectonic model is proposed for the formation of these faults, which are interpreted to have formed syntectonic with the regional convergence of the plates in collision, and could potentially host medium to large magnitude earthquakes in the near future. The expected earthquake focal mechanism “beach ball” on each fault is estimated, which suggests what type of earthquake is possible on the newly mapped faults. The new tectonic interpretation of the region supports the observed seismicity, and correlates with the available geodetic and geologic data.