Foreign, Indian satellite images showed Joshimath sinking

India's National Remote Sensing Centre (NRSC) came out with its report on land subsidence at Joshimath after studying the images captured by the European Space Agency's satellite Sentinel-1 SAR.

The NRSC correlated the identified subsidence zone with India's new Cartosat-2S satellite data acquired by Indian Space Research Organisation (ISRO) on January 7 and 10, the former said in a report.

The NRSC had, on Thursday, put out a preliminary report on the land subsidence showing that the entire Joshimath may sink.

Incidentally, NRSC's preliminary report on Joshimath is not available on its website.

According to NRSC's preliminary report, there were media reports over the last few days, on subsidence occurring at Joshimath and over 700 houses, roads, hospitals and hotels developing cracks.

The Hyderabad based NRSC -- part of ISRO -- processed the imagery of Sentinel-1 SAR to identify the possible location and extent of land subsidence in long and short time intervals -- between April 7, 2022 and November 9, 2022 -- for identification of slow subsidence -- and December 27, 2022 and January 8, 2023 -- for identification of rapid subsidence.

According to NRSC, the identified subsidence zone was correlated with new Cartosat-2S satellite data acquired by ISRO on January 7 and 10.

Meanwhile, the NRSC is analysing in detail the satellite images of the land subsidence at Joshimath, said a senior official of ISRO told IANS.

The NRSC had, on Thursday, put out a preliminary report on the land subsidence showing that the entire Joshimath may sink.

In the images, the entire town, including the Army's helipad and the Narasimha temple, has been marked as a sensitive zone.

On the basis of ISRO's preliminary report, the Uttarakhand government is conducting rescue operations in danger-prone areas and the people in these areas are being shifted to safer places on priority.

According to the report, the land subsidence was slow between April and November 2022, during which Joshimath had sunk by 8.9 cm.

But between December 27, 2022 and January 8, 2023, the intensity of land subsidence increased and the town sank by 5.4 cm in these 12 days.

The satellite images show that the Joshimath-Auli road is also going to collapse due to the land subsidence.

Crown of the subsidence is located near Joshimath-Auli road at a height of 2180 m, NRSC said.

Although scientists are still studying the cracks that appeared in the houses and roads after the land subsidence in the town, the findings in the primary report of ISRO are frightening.

According to NRSC, analysis of temporal InSAR is ongoing to identify landslide kinematics and results will be further updated.