Research Projects

The Eastern Himalayan Syntaxis (EHS) is characterized by significant seismic activity, having produced the notable 1950 Assam earthquake (Ms 8.7, later revised to Mw 8.4, Ambraseys & Douglas 2004), which is the largest recorded in the Himalayas. This area is classified within zone V, indicating the highest level of vulnerability on India's seismic zoning map (BIS 2002). The EHS represents a complex triple junction where the Indian and Eurasian Plates converge with the northern extremity of the Burmese Platelet (Curray 1989). At the eastern terminus of the Himalayan orogeny, a critical tectonic transition occurs, shifting from collisional dynamics to the north, which contributes to the uplift of the Tibetan Plateau, while also facilitating escape tectonics in Southeast Asia via strike-slip faults (Holt 1991; Molnar 1990; Beaumont et al. 2004; Misra 2009; Hazarika et al. 2013). The Siang antiform and the Mishmi Hills encompass a significant portion of the EHS, with the Mishmi Hills region emerging at the convergence of the Indian plate to the west, the Eurasian plate to the east and north, and the Burmese plate to the south. The Siang antiform, also referred to as the Siang window, serves as the focal point of the Syntaxis (Singh 1993; Acharyya 1998). The northeastern region of India has experienced two significant earthquakes, both exceeding a magnitude of 8.0: the Shillong earthquake on June 12, 1897 (Ms 8.7; Oldham 1899) and the Assam earthquake on August 15, 1950 (Tillotson 1951; Ben-Menahem et al. 1974). In addition to these major seismic events, the area has recorded over 20 substantial earthquakes (M>7.0) (Nandy 2001; Kayal 2008). The 1950 Assam earthquake (Ms 8.7) stands as the largest instrumentally documented event in the Himalayas, resulting in extensive destruction across upper Assam, the Mishmi Hills, and the Abor Hills (Podder 1950). Consequently, enhancing our understanding and investigating the tectonic framework concerning the seismicity patterns and structural variations for effective seismic hazard assessment beneath the Siang window is crucial. Previous studies have primarily focused on the source parameters of earthquakes based on seismological data collected by various institutions; however, limited research has been conducted on the structural analysis beneath this region utilizing teleseismic data. Therefore, employing modern seismological techniques, such as shear wave splitting through S/SKS/SKKS and Ps phase analysis, alongside recorded seismological data from various seismic stations in the Siang Valley, will facilitate an investigation into the true nature of crustal and upper mantle deformation patterns, as well as the direction of Absolute Plate Motion (APM) beneath these seismic stations. A comprehensive understanding of the seismic structure and source parameters in this area will enable precise seismic hazard assessments, thereby mitigating risks and providing significant insights into the rupture zone.