were detected by seismic instruments that were part of a global network of instruments. Seismic vibrations produced by the other two slides showed up well on regional networks.
When Ekström and colleague Colin Stark analyzed the seismic data associated with those major landslides, they realized that certain characteristics of the slumps were contained in the ground motions — similar to the way that researchers can use seismic data to estimate the size of a quake and the directions. For instance, when rock falls off a mountainside, the peak is suddenly lighter — so, according to Newton's laws of motion, the mountain springs upward and away from the falling rock, causing initial ground motions that reveal some characteristics of the landslide.
And because seismic data offer clues about how landslides unfold, it may help researchers develop better models of how landslides behave. “People rarely see large landslides happen; they typically only see the aftereffects,” Ekström notes.
Indeed, Ekström and Stark's analysis revealed that a set of landslides that fell onto the Siachen Glacier near the IndiaPakistan border in September 2010 actually included seven slides that occurred over a period of 4 days. “If we'd only seen this deposit in the field, we'd likely have thought it was formed by one or two landslides,” Ekström says.
Although some landslides fortunately don't affect people immediately, they can have longterm effects. If researchers have a way to identify such landslides quickly, they can possibly minimize damage and loss of life.
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