Research suggests earthquakes increase landslide risk

POTSDAM, Germany, Aug. 24 (UPI) -- The disruption and fracturing of rocks near earth's surface as the result of an earthquake momentarily heightens the risk of landslides.

In the wake of a severe earthquake, mountainous regions become up 20 times more likely to experience a landslide -- a risk that is exacerbated by heavy rains, but which fades over time as the landforms heal their fractures and stabilize.

The revelation sounds obvious, but geologists have for years tried to sort out how various factors affect the risk of landslide. It's no an easy task.

"The main difficulty was that one must distinguish between the meteorological and the seismic causes of landsliding," Marc Odin, a researcher at Germany's GFZ German Research Centre for Geosciences, explained in a press release. "Heavy rain can also produce landslides and can enhance landsliding after an earthquake."

But using satellite imagery, researchers in Germany, France and Japan were able to reconstruct the history of four main mountain regions in the wake of major earthquakes. Their analysis showed that landslides were more likely, both on their own and as a result of heavy rains, in the wake of serious rumbles.

Maybe more interestingly, the data also showed that the heightened risk of landslides fades as the background hazard potential returns over a period of one to four years.

"We analytically separated the effect of the rain from the seismic activity and so were able to determine that the decrease of landslides through time is based on an internal healing process of the landscape," said Odin.

Scientists on the project are currently using their research -- published this week in the journal Geology -- to inform their ongoing studies in the Himalayas, as they model the short and longterm geological effects of this year's devastating earthquakes in Nepal.

"We had the chance to start a series of measurements directly after the quake and continue for the next few years," said Niels Hovius, head of the Geomorphology program at GFZ.