Four major unknown active faults identified, using satellite data, in India and Pakistan portions of NW Himalaya

Abstract

New mapping through geomorphic analysis of tectonic landforms using a variety of freely available satellite data, including shuttle radar topography and Google Maps, has revealed four major curvilinear ~NW–SE trending faults in NW Himalaya regions of India and Pakistan. From north-west to south-east, these are named as Mawer, Tunda, Gulmarg, and Mughal Road fault zones. Some of these faults show evidence of oblique faulting where thrusting is accompanied by a small component of sinistral strike–slip faulting, and this possibly increases towards south-east. The active nature of deformation on these faults is demonstrated by occurrence of triangular facets, fault rupture scarps, topographic breaks, displaced ridges, shutter ridges, deflected drainages, plus uplift and back tilting of Holocene sedimentary deposits. This is further supported by the fact that these fault traces truncate the previously mapped active structures such as Kashmir basin/Balapore fault and main boundary thrust. The abrupt termination of most of these faults in north-west indicates a strong structural control. These faults are active, and their dimensions and geometrical configurations indicate their potential to host major earthquakes that could be similar or greater than what we witnessed during Kashmir earthquake of 2005. Further, active deformation is also mapped within Udhampur Piggyback basin, which lies within the Riasi fault system in Jammu and Kashmir, NW Himalaya. The emergent thrusting further suggests splay faulting from one of the branches of the Riasi fault system (Mandili-Kishanpur thrust). The structural configuration of the basin indicates a possible structural control on the formation and deformation of the basin. The geomorphic expression of active faulting is manifested in the overall morphology of the oval-shaped basin (similar to Kashmir basin in NW Himalaya). The shape is structurally controlled by faults as the whole of the basin is riding on Riasi fault system. Within the valley, the active faults are only visible on the ~SE portion. This has divided the basin into two distinctive geomorphic divisions: SE and NW domains. These domains are delineated by a structural break that could be ~NE–SW trending fault zone because the mapped faults do not continue beyond this topographic break in the basin. And since the SE tectonic domain is faulted, the streams are deeply incising into the bedrock forming deep canyons. The tributaries are short because their lengths are trimmed by the faults. Thus, the tributaries on the hanging wall have permanently lost their headwater source and are orphaned. Such geomorphic features are not visible in the NW domains, which have not been faulted, and thus, the streams are following the natural slope. All the streams feed the basin merge into a major stream (Tawi River) that cuts through the anticlinal ridge of Suruin–Mastgarh anticline. This river roughly follows the interpreted ~NE–SW trending topographic break, which could mean that it follows a fault. Such an interpretation is backed by the evidence that the anticlinal ridge is only broken at this portion of the ridge.