An international team of scientists has shed new light on the earthquake that devastated Nepal in April 2015, killing more than 8,000 people. Their work, published in the journal ‘Nature Geoscience’, shows that a sprained regional fault line beneath Nepal explains why the highest mountains of the Himalayas grow between earthquakes. This has created a ramp twisting 20km below the surface, with the material constantly pushed upwards and raising the height of the mountains.
The researchers, from the UK Centre for Observation and Modelling Earthquakes, Volcanoes and Tectonics (COMET, for its acronym in English), as well as academics from the United States and France, also show that the fault rupture stopped 11 kilometers below Kathmandu, indicating that another big earthquake could . take place in a shorter time than one would ever think term
The lead author, Dr. John Elliott, University of Oxford, UK, COMET team member, explains: “Nepal has one of the highest mountain ranges in the world that have been built up over millions of years because of the collision of India with Asia. But the way the mountains grow and when it occurs is still debated. “
” We have shown that failure below Nepal has a twist, creating a ramp of a meter 20km. The material is continually being pushed to the ramp, which explains why it is that mountains are growing in the decades before the quake. The earthquake itself then reversed, the mountains dropping down again when the pressure is released, and when the crust was broken in April 2015, “he adds.
Sinking in the earthquake
> “Using the latest satellite technology, we were able to accurately measure changes in elevation of the land throughout the eastern half of Nepal. The highest peaks are reduced by up to 60 cm in the first seconds of the earthquake, “he explains. Mount Everest, more than 50 kilometers east of the quake zone, was too far to be affected by the collapse seen in this event.
Dr Pablo Gonzalez of the University of Leeds, member COMET team, emphasizes: “We have successfully traced the earthquake using satellite technology in a very difficult mountainous terrain. We have developed new algorithms for processing lighter displacement maps, which revealed the geometry of the cross most likely fail. This geometry makes sense in the puzzling geological observations. “
Another key finding of the study shows that the fault rupture reached 11 kilometers below Kathmandu, leaving an upper portion remains intact.
“By using high-resolution satellite images, we have shown that only a small amount of the quake reached the surface. This is surprising for a major earthquake as well, which normally would be expected that failure left a significant mark on the landscape. This makes it a challenge to try to find the latest earthquake ruptures as they may be hidden “, says Elliott.
The failure has not yet been broken
” We found that the earthquake rupture He stopped April 11 kilometers below Kathmandu and this sudden break due to damage to the failure of interactions with major faults in the region. This is important because the top half of the fault has not yet been broken, but is continually erecting more pressure over time as India continues hitting Nepal, “he explains.
As this part of the fault is closer to the surface, the future breakdown of this top has the potential for a much greater impact in Kathmandu if you break an event similar to the April 2015 size.
The work in other earthquakes it has been suggested that when a break in this way, it may take years or decades before they resume, instead of centuries would normally expect. “Unfortunately, there is no way to accurately predict when another earthquake will occur,” concludes
Source:. Abc. is
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