Neotectonic characterization of the Narmada-Son Fault (NSF) using field and GPR data, Gujarat, western India

The Narmada-Son Fault (NSF) is an ENE-WSW trending crustal-scale fault zone transecting through the central part of the Indian plate. Previous studies on the NSF in its western extremity in Gujarat have provided evidence for tectonic activity along with the NSF throughout Cenozoic under the influence of compressive stresses. In this article, we attempt to delineate Late Quaternary tectonic activity and near-surface characterization of NSF zone using Ground Penetrating Radar (GPR) and field studies. Earlier workers have envisaged that the NSF in Gujarat is divisible into four segments bounded by cross-faults. The intensity of Late Quaternary activity is highly variable in various segments. Maximum intensity is observed in segment II where all north-flowing streams crossing the NSF zone, including Nandikhadi River show, > 50 m incision in Deccan Traps and alluvial sediments. The Nandikhadi River shows three significant falls and several rapids in trappean lava flow in a short stretch of similar to 1.5 km from the scarps. Basaltic exposures in this river provide field constraints for the location and nature of the NSF zone. GPR and field data along its length show that the NSF is a high angle south-dipping reverse fault that conforms to available seismic data.