Steep mountains produce some of the biggest landslides on earth but in such rugged terrain who’s around to notice? These monster backcountry slides are now gaining attention from far-away scientists, aided by a global network of seismic stations, earth-orbiting satellites and the crowd-sourcing power of the internet.
Once a month or so, a landslide packs enough power that it moves the global seismic network’s needles. In May, seismographs recorded two massive slides–in the Himalayas of Nepal and Saint Elias Mountains of Alaska. From computers in Palisades, N.Y., scientists at Columbia University’s Lamont-Doherty Earth Observatory analyzed the evidence to piece together both events.
In Nepal, a flash flood on May 5, in the popular Annapurna trekking region near Pokhara, swept away an entire village. News reports suggested that a huge landslide might have blocked the Seti River, triggering the flood. Colin Stark, a geophysicist at Lamont-Doherty, read the story on landslide expert David Petley’s blog and wondered if the event had been big enough to generate seismic waves. Stark and his Lamont colleague, Göran Ekström, checked Lamont’s catalog of big earthquakes. Sure enough, the Global Seismic Network had picked up the signal at about 9:10 am on May 5, 2012. “You could tell right away it didn’t look like a tectonic event,” said Stark. “This was a landslide.”