Although massive quakes have often hit the region, with four tremors of at least magnitude 7.8 in the 20th century, none were believed to have broken the Earth's surface, but new research has shown two -- the 1255 quake that killed King Abhaya Malla and a 1934 earthquake -- left visible evidence on the land.
Signs of these past ruptures were suggested by old aerial photos of the region and confirmed during field trips.
This concrete evidence of past earthquakes, researchers said, will improve predictions of what hazards people in the area -- the population density in some parts of the Himalayas region is similar to that of New York City -- might face in the future.
"Researchers will now be better able to judge earthquake risks in the area," researcher Laurent Bollinger, a seismologist at France's Commissariat on Atomic Energy, told OurAmazingPlanet.com.
The research has been published in the journal Nature Geoscience.