Shallow subsurface mapping of active faults using GPR in the seismically active Kachchh palaeo-rift basin, Western India: Implication for neotectonic activity

Abstract

We present the results of our GPR and field based studies along the E-W trending Kachchh Mainland Fault (KMF), South Wagad Fault (SWF) and Gedi Fault (GF) that have prominent control on the landscape and ongoing seismic activity of the Kachchh palaeo-rift basin. The Subsurface Interface Radar-20 (SIR-20) GPR system of GSSI, USA alongwith 200 MHz, 100MHz and 80 MHz antenna was used to laterally map the near surface trace and the shallow subsurface nature of the faults. The KMF is found to be a steep northward dipping normal fault that becomes reverse in two segments. The SWF is revealed as a south dipping normal fault. The GF is largely a steep dipping reverse to vertical fault. The GPR data along with field evidences of neotectonic activity that include stratigraphie development of Quaternary sediments, variable incision and sediment deformation, suggest a dominantly N-S oriented compressional stress environment along the active faults of Kachchh basin. However, the distribution, accommodation and release of stresses are not uniform along the faults as they are cut across by oblique slip transverse faults. We infer that the understanding of ongoing seismic activity in the region is complicated by the multiple seismic sources and the segmented nature of the faults.