A house covered in sludge in the aftermath of the August 26 flash flood, at Betrawati Bazaar in Nepal’s Rasuwa district on September 28. (AFP)
The massive ice-rock collapse that triggered Nepal’s devastating Aug 26 Bhote Koshi-Trishuli flood sent a torrent surging at speeds up to 163kmph — faster than Pakistani pacer Shoaib Akhtar’s world-record delivery of 161.3kmph against England in the 2003 Cricket World Cup. The collapse also generated seismic waves detected as far as 19,000km — almost half the globe — away, while more than 60 smaller seismic events were recorded in the preceding two weeks, including a magnitude 2.5 tremor just 17 minutes before the disaster, the first peer-reviewed seismic study of the catastrophe found. Published in scientific journal Seismica, the research was led by Nepalese seismologists Lok Bijaya Adhikari and Shiba Subedi, along with 17 other scientists from seven countries. Scientists analysed seismic recordings from 45 monitoring stations in Nepal and Tibet, selecting 19 with high-quality data, alongside satellite imagery and hydrological observations to reconstruct the sequence of events. Researchers also identified more than 60 smaller seismic events in the fortnight before the collapse, including a magnitude 2.5 tremor just 17 minutes and four seconds earlier, less than 10km from its source.
Scientists suggested some of these events might have been slide-quakes associated with unstable rock or ice, but they could not establish a causal connection with the disaster.
It found that seismic monitoring could help detect catastrophic mountain collapses and provide crucial warning time to communities downstream, although researchers could not establish whether the earlier tremors were precursors to the disaster.