Over the last few days, several media reports have highlighted about the subsidence issues that are occurring at Joshimath. Due to landslide-related creep, cracks have appeared in around >700 houses. Roads along with the hotels and hospitals present there have developed cracks.
The identified subsidence zone was correlated with new Cartosat-2S satellite data acquired by ISRO on 07 and 10 Jan 2023. This study is published by National Remote Sensing Centre, Indian Space Research Organisation.
Here are the observation was processed using the DInSAR technique to identify the possible location and extent of land subsidence in long and short time intervals:
•Slow subsidence up to ~ -9 cm within the Joshimath town is recorded over a period of 7 months, between April and November 2022.
• Between 27th December 2022 and 8th January 2023 (possibly on 2nd January 2022 as per eyewitness reports) a rapid subsidence event was triggered.
• The region subsided around ~ -5 cm within a span of a few days and the areal extent of subsidence has also increased. But it is confined to the central part of Joshimath town.
• A subsidence zone resembling a generic landslide shape was identified (tapered top and fanning out at base). Crown of the subsidence is located near Joshimath-Auli road at a height of 2180 m.
• Analysis of temporal InSAR is ongoing to identify landslide kinematics and results will be further updated.
