Tectonic variability along the South Katrol Hill Fault, Kachchh, Western India: Insights from geomorphic indices

Kachchh is one of the most seismically active intraplate regions in the world, which has produced several major earthquakes in historical period. Katrol Hill Fault (KHF) is one of the active faults of Kachchh. The Southern Kachchh Mainland is delimited by KHF in north and Gulf of Kachchh in south. Several studies have revealed the geomorphology and concluded that the southern Kachchh Mainland is a south dipping tilt block structure, which is sliced into two blocks by an E-W oriented South Katrol Hill Fault (SKHF). Here we employ geomorphic indices to study the geomorphic evidences of South Katrol Hill Fault and evaluate relative tectonic activity along its various segments. We studied seven drainages cutting the SKHF for longitudinal river profile, stream length gradient index, hypsometric integral, valley floor width to height ratio and mountain front sinuosity. These parameters provided useful insights into variation in valley shape, gradient and relief as rivers cut through SKHF. The parameters suggested an uplifting structure namely the SKHF. We classified these parameters into classes of relative tectonic activity from class 1 to class 4 of decreasing tectonic activity to form a parameter called the Relative Index of Tectonic Activity (RITA). The RITA enabled us to classify the SKHF into three segments, of which eastern segment showed highest class of tectonic activity followed by central and western segments.