Paleoseismic evidence of a major earthquake event(s) along the hinterland faults: Pinjore Garden Fault (PGF) and Jhajra Fault (JF) in northwest Himalaya, India

Abstract

Despite identification of numerous active faults in hinterland of the Himalaya, most of the paleoseismological studies are confined to the frontal fault – Himalayan Frontal Thrust (HFT). Barring few examples, no attempt has been made to understand the spatial and temporal pattern of earthquakes occurred along the hinterland faults. In this article we present new data on the coseismic slip and timing of the latest faulting event along the two hinterland faults: the Pinjore Garden Fault (PGF) and Jhajra Fault (JF) in northwest Himalaya. Trench investigations suggest at least two earthquakes along PGF and JF, with the most recent event (MRE) subsequent to 1283 CE–1443 CE and preceded 1600 CE, and around 1223 CE–1442 CE respectively, with observed single event and multi-event slip of 4.26 m and 12.7 m on PGF. The timing of the latest event deduced from the previous trenches (Hajipur to Rampur Ganda) indicates striking coherence with those along the hinterland faults (PGF and JF). We propose that the hinterland faults might have been reactivated by an independent earthquake event between 1283 CE and 1600 CE, just like the 1905 Kangra, 2005 Kashmir, 2015 Nepal earthquakes, which failed to rupture the front but produced surface deformation along the hinterland faults. The loading of the un-ruptured not defined portion of MHT with the residual stress along with constant convergence between the plates during the medieval period must have facilitated another earthquake, rupturing the frontal thrust within 100–300 years of time frame. Our results support the evidence that northwest Himalaya must have hosted multiple large magnitude earthquakes between 1200 CE–1600 CE but seismic quiescence now raises an alarm to the society and the government for the earthquake preparedness.