{"id":42639,"date":"2023-01-18T08:30:04","date_gmt":"2023-01-18T08:30:04","guid":{"rendered":"https:\/\/blogs.agu.org\/landslideblog\/?p=42639"},"modified":"2023-01-18T08:44:59","modified_gmt":"2023-01-18T08:44:59","slug":"joshimath-new-insar","status":"publish","type":"post","link":"https:\/\/blogs.agu.org\/landslideblog\/2023\/01\/18\/joshimath-new-insar\/","title":{"rendered":"Joshimath: new InSAR analysis sheds light on active deformation"},"content":{"rendered":"

Joshimath: new InSAR analysis sheds light on active deformation<\/strong><\/h4>\n

In Joshimath<\/a> the landslide crisis continues, imposing a big impact on the people of the town.\u00a0 Apparently the investigation of the landslide is ongoing, although the exact nature of this is unclear.\u00a0 There is a very bold statement from unnamed “scientists” that\u00a0 the situation is getting better.\u00a0 The New Indian Express reports<\/a> that:-<\/p>\n

\u00a0\u201cThe land of the land submergence area in Joshimath is trying to stabilise,\u201d the scientists believe. However, it will take some more time.\u00a0<\/em><\/p>\n

As soon as the summer starts, there will be a positive change in the situation. \u201cThe flow of water in JP Colony of Joshimath, which was happening at a speed of 10 litres per second, is now happening at 1.9 litres per second, which is comforting,\u201d said scientists, who didn\u2019t want to be named.<\/em><\/p>\n

This is slightly odd.\u00a0 First, the summer is a long way hence, and second the summer will bring monsoon rainfall, which is unlikely to help (although it will not necessarily have an adverse effect).\u00a0 Finally, of course, the land is not trying to do anything except obey the laws of physics.<\/p>\n

More importantly, we now have additional insight into the landslide from a new InSAR analysis undertaken using the Sentinel-1 instrument.\u00a0 This has been undertaken by renowned scientists from AUTh<\/a>\u00a0(Aristotle University of Thessaloniki) and\u00a0CNRS-EOST<\/a> (Centre National de la Recherche Scientifique \/ Ecole et Observatoire des Sciences de la Terre \/ Strasbourg) using the SNAPPING PSI Full Resolution service<\/a>.\u00a0 The work has been released online and is freely available<\/a>, with further analyses under way.<\/p>\n

The team has produced two sets of analyses, including a times series for the movement of the slopes.\u00a0 The first examines movement over the period from January 2018 to 31 December 2022:-<\/p>\n

\"3-Dimensional

3-Dimensional view of the Joshimath slope with the SNAPPING Full Resolution PSI results overlaid (background Google Earth). The location of the active units (A, B, C, D) are delimited by white lines. The location of selected PSI targets 1, 2, 3 and 4 are also indicated. Image posted online on the gep-blog<\/a>.<\/em><\/p><\/div>\n

.<\/p>\n

This diagram clearly shows the various landslide units upon which the town is built, and the movement patterns that they display in the long term.\u00a0 It confirms that the deformation is sliding, not subsidence, as expected.<\/p>\n

A really important element of this work is that the team has produced a time series plot for points shown on the diagram above:-<\/p>\n

\"SNAPPING-derived

SNAPPING-derived LoS displacement time series on four points over the Joshimath slope for the period 01\/2018-12\/2022. The temporal evolution of surface motion among the various slope units follows a complex pattern, with different displacement rates. Image posted online on the gep-blog<\/a>.<\/em><\/p><\/div>\n

.<\/p>\n

There are a few things to note here.\u00a0 First, in the long term the different parts of the landslide complex are moving at different rates, which is not unusual.\u00a0 Point 1 is showing large displacements – almost half a metre with continuous creep, although the rate clearly fluctuates with time (this is similar to the results we got for the Utiku landslide in New Zealand<\/a> for example).\u00a0 Other parts of the complex are moving more slowly, and indeed the point highest up the slope is not moving.<\/p>\n

Point 3 shows a significant change in movement rate in late 2021.<\/p>\n

The second analysis undertaken by the team examines movement over the last few weeks:<\/p>\n

\"Unwrapped

Unwrapped differential interferogram computed with the P-SBAS service for the Sentinel-1 ascending track 129 between the acquisitions of December 31, 2022 and January 12, 2023. Unwrapped differential interferogram provides the displacement of the ground in the LoS direction between two acquisitions. The orange and red colors indicate motion far away from the satellite corresponding to the downhill motion of the slope. Contains modified Copernicus Sentinel-1 images, 2022-2023. Image posted online on the gep-blog.<\/a><\/em><\/p><\/div>\n

.<\/p>\n

The analysis shows that three portions of the landslide complex are currently moving, with the highest rates towards the lower part of the slope.\u00a0 The boundaries of the movement coincide with the margins of the landslide blocks identifiable from Google Earth.\u00a0 We would expect to see some of the greatest amounts of building damage occurring around these margins.\u00a0 Thus, it is really interesting to compare the above diagram with the map posted to Twitter<\/a> by Thiyagarajan J (@jThiyagu<\/a>) that shows the location of the wards damaged by the landslide:-<\/p>\n

https:\/\/twitter.com\/jThiyagu\/status\/1612090648982851585<\/p>\n

.<\/p>\n

There is a strong coincidence, which suggests that these analyses are starting to pin down in more detail the nature of the landslide problem at Joshimath.<\/p>\n

Movement of landslide complexes such as this is very complex, and we would expect to changes in the rate occurring through time.\u00a0 Thus, great care is going to be needed in interpreting short duration time series data.\u00a0 But, the bottom line is that this slope is unlikely to achieve permanent stability in its current physical state without significant engineering intervention.\u00a0 The current crisis will abate at some point, but the underlying chronic problem, whatever the cause, is likely to remain.\u00a0 That is not to say that all is lost by any means, the immediate crisis will pass, but action is likely to be needed.<\/p>\n

.<\/p>\n

Acknowledgement<\/strong><\/h4>\n

Many thanks to colleagues from \u00a0AUTh<\/a>\u00a0(Aristotle University of Thessaloniki) and\u00a0CNRS-EOST<\/a> (Centre National de la Recherche Scientifique \/ Ecole et Observatoire des Sciences de la Terre \/ Strasbourg) for making this analysis available online.<\/p>\n","protected":false},"excerpt":{"rendered":"

Joshimath: a new InSAR analysis sheds light on active deformation over the last few months and the last few weeks <\/p>\n","protected":false},"author":22,"featured_media":42642,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_members_access_role":[],"_members_access_error":""},"categories":[3],"tags":[469,18,5,4898,30722,959,25,72],"class_list":["post-42639","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-landslide-report","tag-featured","tag-himalayas","tag-india","tag-insar","tag-joshimath","tag-landslide-report","tag-satellite","tag-south-asia"],"_links":{"self":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/42639","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/users\/22"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/comments?post=42639"}],"version-history":[{"count":0,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/42639\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media\/42642"}],"wp:attachment":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media?parent=42639"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/categories?post=42639"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/tags?post=42639"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}