Nepal earthquake caused fewer landslides than expected: study

Fewer landslides resulted from the devastating earthquake that struck Nepal in April this year than expected, scientists including one of Indian-origin have found.
In addition, no large floods from overflowing glacial lakes occurred after the magnitude 7.8 quake, which struck near the town of Gorkha, Nepal on April 25, researchers said.
"It was a really bad earthquake - over 9,000 fatalities in four countries, primarily Nepal," said Jeffrey Kargel from the University of Arizona.
"As horrific as this was, the situation could have been far worse for an earthquake of this magnitude," he said.
The researchers including those from Global Land Ice Measurements from Space (GLIMS) used satellite imaging to help find where landslides had happened.

The team's initial efforts focused on possible earthquake effects on Himalayan glaciers, but quickly expanded to searching for post-earthquake landslides.

The scientists including Umesh Haritashya of the University of Dayton in Ohio, along with the NASA Applied Sciences Disasters group used remote sensing to help document damage and identify areas of need.
The scientists requested that several satellites take images of the region to enable the systematic mapping of landslides.
They then selected which ones to analyse and organised into six teams to scrutinise the vast earthquake-affected region for landslides.
More than 10 satellites from four countries provided images and other data so the analysts could map and report the various geological hazards, including landslides, that resulted from the earthquake.

Computer models were used to evaluate the likelihood that the downstream edges of glacial lakes would collapse and flood villages and valleys below.
The 4,312 landslides that happened within six weeks after the quake were far fewer than occurred after similar-magnitude quakes in other mountainous areas.
The team also surveyed 491 glacial lakes and saw only nine that were affected by landslides. Satellite images did not show any flooding from those lakes.
In addition to identifying the locations and severity of landslides, the researchers found an unexpected pattern of where the landslides happened.
The researchers used satellite radar imagery to create a map of the terrain that dropped during the earthquake and where land surface had risen.

The Earth's surface dropped almost 1.4 metres in some places and rose as much as 1.5 metres in others.
"Seismologists recorded relatively less shaking with seismometers in Kathmandu and other locations, and the smaller number of landslides suggests the shaking may have been reduced in the whole area," said Eric Fielding from NASA's Jet Propulsion Laboratory in US.
The findings were published in the journal Science.