Active Fault and Paleoseismic Studies in Kangra Valley: Evidence of Surface Rupture of a Great Himalayan 1905 Kangra Earthquake (Mw 7.8), Northwest Himalaya, India

Our findings suggest that interseismic strain accumulated south of the fault ramp under the Higher Himalayas was not only released periodically along the Himalayan frontal thrust (HFT) during large-magnitude earthquakes, but also along the active faults in the hinterland. The 4 April 1905 Kangra earthquake (M-w 7.8) killed more than 20,000 people and destroyed the towns of Kangra and Dharamsala in northwest Himalaya. In spite of its large magnitude, with a maximum intensity X on the Rossi-Forel intensity scale recorded in the epicentral area, no surface rupture was reported, and no focal mechanism is available. This article uses satellite imagery and field mapping to identify an active rightlateral strike-slip fault, named the Kangra Valley fault (KVF). We infer that the KVF represents the surface rupture of the 1905 Kangra earthquake, extending west-northwest-east-southeast and east-west for similar to 60 km. It cuts through the Kangra and Sihunta Valleys and is capable of producing M-w >= 7.2 earthquakes. Existence of the KVF in the Kangra re-entrant is indicative of oblique convergence and slip partitioning between the Main Boundary thrust in the north, the Jawalamukhi thrust in the south, and a strike-slip fault in the northwest Himalaya. Paleoseismic investigations revealed evidence of at least four earthquakes on the KVF. Event I (oldest) occurred before 900 B.C. or between 900 B.C. and 2500 B.C.; Event II occurred between 100 B.C. and 80 B.C.; penultimate Event III occurred around A.D. 800 and A.D. 1000; and, the most recent event, Event IVoccurred after A.D. 1620 and before A.D. 1940 and is likely the 1905 Kangra earthquake (M-w 7.8). A longer recurrence along the KVF is inferred between older paleoearthquake Events I and II, and a shorter interval of 1050 +/- 150 years is inferred between younger events (II, III, and IV). Because the strain during the 1905 Kangra earthquake was released along the KVF, potential for large-magnitude earthquakes in northwest Himalaya along the HFT still remains.