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Ground deformation on a regional to local scale is the consequence of a wide range of natural processes such as tectonic and anthropogenic activities. Globally, the over-extraction of groundwater and hydrocarbon exploitation are the primary causes of ground subsidence. The current study demonstrates regional scale ground subsidence analysis of the Dibrugarh and Digboi regions of Brahmaputra alluvial plain, Assam, Northeast India. To understand the ongoing surface deformation satellite base, the RADAR technique has been applied using SENTINEL-1A data, which were acquired between 15 October 2015 to 25 January 2022. The assessment carried out via the time series analysis of the radar data suggests that the Dibrugarh area is subsiding at a rate of ~5 mm/yr, whereas the Digboi is deforming at a much faster rate (±22 mm/yr) than Dibrugarh. The presence of active faults in the subsurface and associated deformation is another reason for active ground subsidence. The outcomes of the current study validate that the study area is currently undergoing active subsurface deformation caused by both endogenic as well as exogenic processes. Furthermore, our Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) and satellite-based analysis suggest that the over-exploitation of the natural resources is enhancing the rate of deformation in the Brahmaputra alluvial plain in the northeast of India. [ABSTRACT FROM AUTHOR]

The co-seismic deformation of the 28th April 2021 Assam earthquake with a magnitude of 6.4 has been investigated using the Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR). The results obtained from the PSInSAR are validated with the results of the Global Positioning System (GPS). It is observed that the co-seismic deformation of the earthquake is not visible because of the atmospheric noise. Therefore, we used the Sentinel-1 time-series data of the area to minimize the atmospheric noise effect the data using the Atmospheric Phase Screening (APS) processing of Sentinel-1 time series data. The time-series analysis shows minor changes that occurred during the earthquake. Firstly, the detection of coherence-based changes was carried out to identify the most affected areas, caused by the earthquake. The results of time series analysis suggest that the region located to the north of the Brahmaputra River is subsiding at a much faster rate (−25 to -75 mm/y) than its southern counterpart, where the southern part is subsiding with an average velocity of −0.1 to −15 mm/y. The subsided locations identified using the PSInSAR are further confirmed by the presence of liquefaction features, ground cracks, and tilted buildings related to post-liquefaction ground settlement. To see the deformation along the Bomdila Fault (BF), re-analysis of the available GPS results has been carried out and the derived results reveal a significant amount of deformation (∼4 mm/y) associated with BF and Jorhat Fault (JF); whereas the deformation associated with Kopili Fault (KF) is 3.14 mm/y. Further, our results suggest the presence of compressional strain in the BF zone, while extensional strain in the KF zone. The earthquake focal mechanism analysis suggests that the event of the April 2021 was primarily associated with the BF rather than the KF. • We investigated co-seismic deformation caused by 28th April 2021 Assam earthquake. • Time-series analysis reveals significant amount of ground subsidence in the area. • We identified higher subsidence rates towards the north of Brahmaputra River • GPS result suggests that the Bomdila fault (BF) is deforming much faster than KF. • The identified co-seismic deformation of BF is ∼4 mm/y and 3.14 mm/y along the KF. [ABSTRACT FROM AUTHOR]