Active Low-Angle Reverse Fault and Wide Quaternary Deformation Identified in Jhura Trench across the Kachchh Mainland Fault, Kachchh, Gujarat, India

Abstract

The Kachchh region has suffered from at least four damaging moderate to large earthquakes since the 17th century. However, none of these earthquakes except the 1819 Allah Bund earthquake accompanied surface rupture. Even the recent 2001 Bhuj earthquake with Mw7.6 occurred on a blind fault. Several faults in the Kachchh viz. the Island Belt Fault, the Kachchh Mainland Fault (KMF), and the Katrol Hill Fault were suggested to be active during Late Quaternary time by previous studies. But there is no such supportive evidence available in the historical documents; also none of recent studies except ours (Morino et al., 2007, Malik et al., 2008, and Morino et al., 2008) reported ground truth that these fault are active. We in our earlier paper reported faulting in Late Pleistocene to Holocene age sediment near the Lodai Village along the KMF. To confirm further active faulting along the KMF, paleoseismic investigation near Jhura Village about 30 km west of Lodai revealed an active fault displacing overbank deposits of Kaila River. Two fault strands F1 and F2 were identified in the trench. The northern F1 shows a low-angle reverse fault with inclination of 15° towards the south. At least two faulting events were inferred on the basis of upward fault termination with clear angular unconformity. The net-slip during a single faulting event considering deformation on the hanging wall of F1 fault is over 5 m.