The Nepal earthquake: Partial unzipping of the Himalaya

The devastating Nepal earthquake released stress on only a portion of the Main Himalayan Thrust fault, reports a study published online in Nature Geoscience. The research suggests that the western portion of the Main Himalayan Thrust fault must now be closely monitored because it has the potential to host a large earthquake in the future.

On 25 April 2015, a magnitude 7.8 earthquake struck central Nepal, killing more than 9,000 people and flattening entire villages. The earthquake is thought to have occurred on the Main Himalayan Thrust fault -a fault that has produced great earthquakes in the past. This fault was known to be locked in places and accumulating stress with the potential to slip in a large earthquake.

Jean-Philippe Avouac and colleagues use seismic and satellite data to reconstruct the evolution of the April 2015 earthquake. They find that the quake initiated northwest of Kathmandu and propagated about 140 km eastwards beneath the city, but did not reach the surface. The earthquake unzipped the lower edge of the locked zone in the Main Himalayan Thrust fault. However, parts of the fault farther west did not rupture and remain locked. Furthermore, the earthquake may have transferred stresses into western and shallower parts of the crust, which may help to facilitate future rupture of these regions.

doi: 10.1038/ngeo2518

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