The Eastern Himalaya is one of the most tectonically active regions in the world due to the ongoing convergence between the Indian and Eurasian plates. Understanding the spatial pattern of surface deformation associated with earthquakes is crucial for interpreting fault kinematics and regional tectonics. In this study, Differential Interferometric Synthetic Aperture Radar (DInSAR) techniques are applied to Sentinel-1 SAR data to investigate the ground deformation produced by the 5 January 2022 earthquake near Gangtok, Sikkim in the Eastern Himalaya. Pre- and post-seismic SAR images acquired from ascending and descending satellite orbits were processed using the SNAP platform to generate interferograms and compute Line-of-Sight (LOS) displacement. The LOS measurements were further decomposed into vertical and east–west horizontal components to better constrain the deformation field. The interferometric results reveal significant localized ground deformation, with pronounced phase fringes concentrated north of the epicentre. The descending orbit data show stronger deformation signals, indicating a dominant east–west horizontal displacement component. Decomposition of LOS displacement suggests substantial westward horizontal motion accompanied by localized vertical subsidence near the epicentral region and uplift in adjacent areas. The spatial distribution of deformation indicates an oblique-slip faulting mechanism, involving both strike-slip and dip-slip components. The observed displacement pattern is consistent with reactivation of a steeply dipping pre-existing fault structure that may be associated with the tectonic framework responsible for the 2011 Mw 6.9 Sikkim earthquake. The study demonstrates the effectiveness of DInSAR techniques for detecting subtle earthquake-induced deformation in mountainous terrains where ground observations are limited. These results provide new insights into fault behaviour and stress release mechanisms in the Sikkim Himalaya and contribute to improved understanding of seismic hazard and active tectonics in the Eastern Himalayan region.
Dipanjan Bhattacharjee (Wed,) studied this question.