There is a possibility of a more severe earthquake in the Himalayas \u2013 although it isn\u2019t certain when \u2013 than the 7.9-magnitude tremblor that devastated Nepal on April 25, according to the latest research.
\n\u201cWe are most worried about it,\u201d Stanford University geophysicist Simon Klemperer told IndiaSpend, referring to the section of what is called the Main Himalayan Thrust, the primary faultline or fracture along which India grinds into Asia at about 2 cm every year.
\nAbout 400-km long, that section of the fault lies west of Gorkha \u2013 epicentre of the Nepal earthquake \u2013 and extends to the Kumaon-Garhwal region of India.<\/p>\n
A slew of papers \u2013 Geophysical Research Letters, Nature Geoscience, Science \u2013 have provided a better understanding of what is now called the Gorkha earthquake, the geological stress that caused it and which was only partially released.
\nJean-Philippe Avouac, director of the Tectonics Observatory at Caltech in the US and author of many recent studies, said data collected over the last 10 to 15 years reveal that everywhere along the Himalayan arc, the Main Himalayan Thrust faultline is locked from the surface to beneath the Himalayas over a distance of about 100 to 120 km.
\nThis is not good news because faults often move or \u2018creep\u2019, without posing any danger. But, in the Himalaya, there is no \u2018creep\u2019 as such, which means that strain-energy is building up.<\/p>\n
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What the Gorkha Earthquake Did<\/strong> The second earthquake, which pushed down some high peaks northeast of Kathmandu, occurred at the eastern edge of the Gorkha quake and along the same fault, so \u201cstress was likely much increased by the first event\u201d, said Roland Burgmann, a professor of earth and planetary science at the University of California at Berkeley. As Himalayas Convulse, Ancient Tectonic Forces are Renewed<\/strong> Eric Kirby, an associate professor of earthquake geology and active tectonics at Oregon State University, used the analogy of a concrete block being dragged over a rough, dirt road. The heavier the block, the harder it is to move. Why the Himalayas Dive and Rise<\/strong> Plates, Earthquakes and Aftershocks Reveal What Might Be<\/strong> Source:\u00a0www.thequint.com<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":" There is a possibility of a more severe earthquake in the Himalayas \u2013 although it isn\u2019t certain when \u2013 than the 7.9-magnitude tremblor that devastated Nepal on April 25, according to the latest research.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-1459","post","type-post","status-publish","format-standard","hentry","category-third-pole"],"_links":{"self":[{"href":"https:\/\/tibetnature.net\/en\/wp-json\/wp\/v2\/posts\/1459","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/tibetnature.net\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/tibetnature.net\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/tibetnature.net\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/tibetnature.net\/en\/wp-json\/wp\/v2\/comments?post=1459"}],"version-history":[{"count":2,"href":"https:\/\/tibetnature.net\/en\/wp-json\/wp\/v2\/posts\/1459\/revisions"}],"predecessor-version":[{"id":1461,"href":"https:\/\/tibetnature.net\/en\/wp-json\/wp\/v2\/posts\/1459\/revisions\/1461"}],"wp:attachment":[{"href":"https:\/\/tibetnature.net\/en\/wp-json\/wp\/v2\/media?parent=1459"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/tibetnature.net\/en\/wp-json\/wp\/v2\/categories?post=1459"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/tibetnature.net\/en\/wp-json\/wp\/v2\/tags?post=1459"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\nThe Gorkha earthquake rearranged the region horizontally and vertically, pushing Kathmandu up by a meter and a half and pushing down many of the surrounding high peaks by between half a metre to a metre, Tim Wright, a geophysicist at the University of Leeds in the UK, told IndiaSpend, after examining the latest data.
\nThe second earthquake on May 12, said Wright, \u201cchanged the height of peaks again, causing more subsidence in the high peaks north-east of Kathmandu\u201d.
\nThe area west of Gorkha has not seen a major earthquake for more than 500 years, and a single earthquake of a magnitude of 8.5 or more could cause the crust to slip by as much as 10 metres, or more than twice as severe as in April, when more than 9,000 people died.
\nThese geological displacements are continuing, caused by the activity of the Indian plate \u2013 a raft of the earth\u2019s crust that bears the subcontinent \u2013 as it grinds into what is called the Eurasian plate, the Asian landmass.<\/p>\n
\nCombined with a historical perspective of geological forces at work under the subcontinent, there is now a better idea of the strain accumulated along the boundaries of the Indian and Eurasian plates.<\/p>\n
\nThe Himalayas are a source of large earthquakes along the Himalayan thrust system that bears its name; the tectonic regime is in turn responsible for shaping Earth\u2019s greatest mountains.
\nIn other words, earthquakes are one of the ways in which mountains are formed.
\nThe Indian and Eurasian plates have been in conflict for 50 million years at this collision zone, with the Indian plate diving, northward, under the Eurasian plate. This is why the Himalayas, including Mount Everest \u2013 which was away from the main April earthquake area and moved by no more than a centimetre \u2013 are still growing.
\nAlong the interface between these two plates \u2013 the main faultline \u2013 large earthquakes happen.
\nScientists describe the earthquake cycle as a \u201cstick-slip\u201d: The two plates are stuck for a long time \u2013 often centuries pass between the largest earthquakes \u2013 and then rapidly slip in earthquakes that last seconds or minutes.<\/p>\n
\n\u201cIf you attach a cable to the end of the block, and pull on it with a truck, the block will slide,\u201d said Kirby. \u201cHowever, if the tow rope has some elasticity\u2013that is, it can stretch\u2013then what happens? The rope stretches for a while and the block still does not move. At some point, the strain in the tow rope is large enough that it overcomes the frictional forces under the block, and the block lurches forward.\u201d
\nThe Gorkha earthquake was one such lurch, and scientists fear a bigger lurch is coming, potentially devastating to Himalayan countries but a common blip in geological time.<\/p>\n
\nLike a thick iceberg that floats above the surface of the ocean, the Himalayas and the Tibetan plateau \u201cfloat\u201d higher than the surrounding crust, which slides atop the viscous layer beneath it, the mantle.
\nWhen an earthquake occurs, as on April 25, Standord\u2019s Klemperer explained, \u201cthe Himalayas surge forward across the Indian Plate\u201d, dropping the mountains (including Mount Everest) down.
\nHowever, as landslides and avalanches erode the top of Mount Everest, weight is taken off it, and the earth rebounds. Klemperer used an analogy: \u201cIf you stood on an iceberg and chipped 10m of ice off the top and threw it into sea, you wouldn\u2019t be 10m closer to sea-level, because the iceberg would float back up.\u201d
\nSo, \u201cthe drop-down is not much, and Mt. Everest is in approximate equilibrium\u201d, he said.<\/p>\n
\nAs the Himalayas and southern Tibet (part of the Eurasian plate) ride over the Indian plate, every year, India converges with Asia, growing closer by about 2 cm, said Kirby of Oregon State University.
\nIn 100 years, that translates to 2 metres, and in 1,000 years, to 20 metres. As he further explained, there is some good evidence from French geologists working on these faults that shows that the last earthquake that broke this part of the fault system happened in medieval times (1200-1400 AD). An earthquake in 1934 broke a section farther east along the fault system.
\nSo, prior to the April 25 earthquake, Kirby said, it had been a long time since the last big rupture, long enough that 10 or more metres of convergence between India and Eurasia built up energy along the faultline.
\nAs devastating as it was, the April 25 earthquake appears not to have released all of that energy. The fault slipped, on average, three to four metres, and it does not appear to have ruptured all the way to the end of the fault (at the foot of the Siwalik ranges), as USGS data indicates.<\/p>\n