The Nepal flash floods were triggered by a glacial collapse and not by a 4.4 magnitude earthquake as reported earlier, the US Geological Survey (USGS) said.
The USGS said additional analysis of the long-period seismic waves indicated that the tremors were generated by a glacial collapse and debris flow.
The flash floods originating in Tibet on Wednesday left a trail of death and destruction in Rasuwa and Dhading districts of Nepal, killing 162 people and leaving 750, including 133 Indian nationals, missing.
“This event was initially reported as a magnitude 4.4 earthquake. Additional analysis of nearby seismic stations, long period seismic waves, and satellite imagery led to the determination that the seismic event was instead a glacial collapse and debris flow, and that no earthquake had occurred,” the USGS said in an update to its note on the event.
It also upgraded the magnitude of the seismic event to 5.2 from the 4.4 assessed earlier.
“The USGS determined that the seismic event was a glacial collapse and debris flow that caused subsequent catastrophic impacts downstream,” it said.
Daniel Shugar, an Associate Professor of geomorphology at the University of Calgary in Canada said the flash floods were triggered by a glacier that rolled off a cliff at 5,200 meters.
Shugar compared the satellite images of the region taken on Wednesday and Tuesday, a day before the natural disaster struck Nepal.
“Comparing satellite imagery from yesterday and today, the glaciers in the vicinity do seem to have lost a fair bit of snow in the last 24 hours,” Shugar was quoted as saying by the New Scientist magazine.
“My guess is that snow melt, and glacier ice melt as well, injected a lot of liquid water into the glacier, which percolated down to the bed and lubricated it. That was enough for it to collapse,” he said.
(PTI)
