Seismotectonics of central and NW Himalaya: plate boundary–wedge thrust earthquakes in thin- and thick-skinned tectonic framework

Abstract

AbstractThe tectonic framework of NW Himalaya is different from that of the central Himalaya with respect to the position of the Main Central Thrust and Higher Himalayan Crystalline and the Lesser and Sub Himalayan structures. The former is characterized by thick-skinned tectonics, whereas the thin-skinned model explains the tectonic evolution of the central Himalaya. The boundary between the two segments of Himalaya is recognized along the Ropar–Manali lineament fault zone. The normal convergence rate within the Himalaya decreases from c. 18 mm a−1 in the central to c. 15 mm a−1 in the NW segments. In the last 800 years of historical accounts of large earthquakes of magnitude Mw ≥ 7, there are seven earthquakes clustered in the central Himalaya, whereas three reported earthquakes are widely separated in the NW Himalaya. The earthquakes in central Himalaya are inferred as occurring over the plate boundary fault, the Main Himalayan Thrust. The wedge thrust earthquakes in NW Himalaya originate over the faults on the hanging wall of the Main Himalayan Thrust. Palaeoseismic evidence recorded on the Himalayan front suggests the occurrence of giant earthquakes in the central Himalaya. The lack of such an event reported in the NW Himalaya may be due to oblique convergence.