Joshimath 'sank' 8.9 cm in 7 months, 5.4 cm in 12 days: ISRO and Foreign satellite imagery

Analysis of satellite imagery from Indian and foreign sources has revealed that the extent of 'sinkage' at the Joshimath hilltop city in India's Uttarakhand was a total of 14 cm, over a total time period of 9 months.Located at a height of 6150 feet or 1875 meters, Joshimath town is a gateway to several tourist and pilgrimage destinations in the Himalayas. In recent weeks, cracks have appeared in hundreds of homes, along roads and this has prompted the administration to shift residents out of the area and offer them compensation and carry out detailed studies.

National Remote Sensing Centre (NRSC), a part of the Indian Space Research Organization has analysed both foreign and Indian satellite images of Joshimath and made preliminary observations about the extent of sinkage.A technique to measure land deformation, known as 'DInSAR' (Differential Interferometry Synthetic Aperture Radar)was initially applied to images of Joshimath captured by the European Space Agency's Sentinel-I satellites. The Sentinel constellation of satellites is capable of mapping the entire global landmass on a bi-weekly basis.

Add WION as a Preferred Source

For identifying slow subsidence (sinking), a comparison was carried out between Sentinel image data from 7thApril 2022 and 9thNovember 2022 (7-month duration). For identifying rapid sinking, the image data from 27thDecember 2022 to 8thJanuary 2023 (12-day duration) was compared. It was recorded that the subsidence was around 9 cm during the 7-month period and 5 cm during the 12-day period. It was also pointed out that the area of the sinking has also increased, but remains confined to the central part of Joshimath town.

The NRSC report also mentioned that theCrown of the subsidence is located near Joshimath-Auli road at a height of 2180 m. Theidentified subsidence(sinking) zone was correlated with ISRO's Cartosat satellite data acquired on 7th and 10 January 2023.The NRSC is also carrying out an analysis of temporal InSAR is ongoing to identify landslide kinematics and the results will be further updated. Temporal InSAR is amethod to measure the spatial extent and magnitude of surface deformation.

WATCH WION LIVE HERE