SRINAGAR: A glacial collapse and debris flow, rather than an earthquake, triggered the devastating flash floods that struck Nepal on Thursday, the US Geological Survey (USGS) said, revising its earlier assessment of the event.
The USGS said further analysis of data from nearby seismic stations, long-period seismic waves and satellite imagery established that no earthquake had occurred. It also revised the magnitude of the seismic event from the previously reported 4.4 to 5.2.
“This event was initially reported as a magnitude 4.4 earthquake. Additional analysis … 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.
The glacial collapse occurred in Tibet and triggered catastrophic flooding downstream, leaving a trail of destruction in Nepal’s Rasuwa and Dhading districts. The disaster has killed 162 people, while 750 remain missing, including 133 Indian nationals, according to the report.
The USGS said the seismic event was caused by the glacial collapse and subsequent debris flow, which resulted in catastrophic impacts downstream.
Daniel Shugar, an associate professor of geomorphology at the University of Calgary in Canada, said the floods were triggered by a glacier that fell from a cliff at an elevation of about 5,200 metres.
Comparing satellite imagery from Tuesday and Wednesday, Shugar said glaciers in the area appeared to have lost a substantial amount of snow within 24 hours, New Scientist reported.
He suggested that melting snow and glacier ice may have introduced significant amounts of water into the glacier, which travelled towards its base and lubricated it, potentially contributing to the collapse.
The USGS revision comes as rescue and relief operations continue in the flood-hit areas, where the disaster has caused widespread loss of life and infrastructure damage.
