The first good view of the aftermath of Nepal’s deadly earthquake from a satellite reveals that a broad swath of ground near Kathmandu lifted vertically, by about 3 feet (1 meter), which could explain why damage in the city was so severe. The data also indicate the tallest mountain in the world, Mount Everest, got a wee bit shorter.
The new information comes from Europe’s Sentinel-1A radar satellite. Scientists are racing to interpret the Sentinel data, which were made available today (April 29) just hours after the satellite passed over Nepal. The preliminary data can help guide relief efforts on the ground by identifying areas that were damaged or hit by landslides.
Researchers detected the vertical shift in the ground by comparing before-and-after radar images from the satellite using a technique that produces an image called an interferogram. The resulting images have rainbow-colored areas that represent the movement of the ground between the times each radar image was taken. Each colorful fringe on the European Space Agency’s Nepal interferogram reflects about 1 inch (2.8 centimeters) of vertical movement. The results will be refined in the coming weeks, with as scientists further analysize the images and additional data from satellites become available.
According to the early analysis, a region 75 miles (120 kilometers) long by 30 miles (50 km) wide lifted upward by as much as 3 feet during the earthquake, said Tim Wright, a geophysicist at the University of Leeds in the United Kingdom. This uplift peaked only 10 miles (17 km) from Kathmandu, even though the city was relatively far from the earthquake’s epicenter.
“That’s one of the reasons why Kathmandu has so much damage,” Wright told Live Science.
The radar images reveal that some of the world’s tallest peaks — including Mount Everest — dropped by about 1 inch (2.5 cm), according to the nonprofit UNAVCO, a geoscience research consortium. That’s because the Earth’s crust relaxed in the areas north of the Kathmandu, after the earthquake released pent-up strain.
Still, on the whole, the Himalayas continue to grow to stupendous heights, studies show. Some parts of the Himalayas are rising about 0.4 inches (1 cm) every year, due to the ongoing collision between the Indian and Eurasian tectonic plates.
“This is only one earthquake, and the overall tectonics give you uplift of the mountains,” Wright said.
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