Mt. Everest Shrank as Nepal Quake Lifted Kathmandu
The first good satellite view of Nepal's deadly earthquake could explain why damage in the city was so severe.
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 new information comes from Europe's Sentinel-1A radar satellite. Scientists are racing to interpret the Sentinel data, which were made available Wednesday 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. [See Images of the Kathmandu Uplift & Other Nepal Quake Effects]
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.
The new data from the satellite also confirm what researchers had detected from seismometers: The fault involved in the earthquake ruptured eastward, out from the earthquake epicenter, Wright said. "Presumably, much of the damage will be to the east of the epicenter," he said.
The April 25 earthquake struck on a shallowly-dipping thrust fault that angled only 10 degrees from the surface. The structure of this fault meant the damage was spread over an area of more than 5,600 square miles (more than 14,000 square km).
In size and structure, the magnitude-7.8 earthquake compares most closely to temblors on subduction zones, said Rich Briggs, a geologist with the U.S. Geological Survey in Golden, Colorado. "We don't often see a big, broad bulge at the surface like we see with this one," Briggs said.
Scientists plan to continue monitoring ground changes in Nepal. For instance, the fault did not break all the way up to the Earth's surface, which may mean that some strain that built up prior to the earthquake still needs to be unleashed. The fault could release this energy with more earthquakes or by slowly shifting without triggering major temblors - a phenomenon called creep. Further studies will also help researchers understand how the earthquake stressed other faults on either side of the rupture.
"I think this will give us our clearest insight into the workings of the faults along the Himalayan front," said Stephen Hicks, a seismologist at the University of Liverpool in the United Kingdom.
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A massive earthquake killed more than 3,700 people Saturday as it tore through large parts of Nepal, toppling office blocks and towers in Kathmandu and triggering a deadly avalanche at Everest base camp. Photo: Members of the China International Search and Rescue Team arrive at Tribhuwan International Airport in Kathmandu, Nepal, on April 26.
Officials said the quake was the Himalayan nation's worst disaster in more than 80 years. But the final toll from the 7.8 magnitude quake could be much higher, and dozens more people were reported killed in neighboring India and China. Above, a temple lies in ruins at the Durbar Square in Patan, Nepal.
Tibetan kids eat breakfast supplied by rescue teams in Jilung County of Xigaze City, southwest of Tibet on Sunday.
Photo: Indian bystanders int he city of Siliguri look at a collapsed house following the Nepal earthquake.
Emergency workers fanned out across the Himalayan nation to rescue those trapped under collapsed homes, buildings and other debris. Offers of help poured in from governments around the world, with the United States and the European Union announcing they were sending in disaster response teams. "Deaths have been reported from all regions except the far west. All our security personnel have been deployed to rescue and assist those in need," Bam told AFP. The Red Cross (IFRC) said it was concerned about the fate of rural villages close to the epicenter of the quake northwest of the capital Kathmandu. Photo: Rescuers recover injured from rubble in Nepal's devastated capital city, Kathmandu.
"Roads have been damaged or blocked by landslides and communication lines are down preventing us from reaching local Red Cross branches to get accurate information," said IFRC Asia/Pacific director Jagan Chapagain in a statement. Officials said 10 people were killed when an avalanche buried parts of Mount Everest's base camp in Nepal where hundreds of mountaineers have gathered at the start of the annual climbing season. "We don't have the details yet, but 10 have been reported dead so far, including foreign climbers," Gyanendra Kumar Shrestha, an official in Nepal's tourism department, told AFP. "We are trying to assess how many are injured. There might be over 1,000 people there right now, including foreign climbers and Nepalese supporting staff." Photo: Many neighboring countries felt the earthquake's impact, including India.
AFP Nepal bureau chief Ammu Kannampilly, on an assignment to Everest together with a colleague, was among those caught up in the chaos. "We are both ok... snowing here so no choppers coming," she said in an SMS on an approach to base camp. "I hurt my hand - got it bandaged and told to keep it upright to stop the bleeding." Experienced mountaineers said panic erupted at base camp which had been "severely damaged", while one described the avalanche as "huge". Photo: People work to clear up earthquake damage in Siliguri, India.
"Huge disaster. Helped searched and rescued victims through huge debris area. Many dead. Much more badly injured. More to die if not heli asap," tweeted Romanian climber Alex Gavan from base camp. Kathmandu was severely damaged, and the historic nine-storey Dharahara tower, a major tourist attraction, was among buildings brought down. At least a dozen bodies were taken away from the ruins of the 19th-century tower, according to an AFP photographer who saw similar scenes of multiple casualties throughout the city. "It was difficult to breathe, but I slowly moved the debris. Someone then pulled me out. I don't know where my friends are," Dharmu Subedi, 36, who was standing outside the tower when it collapsed, said from a hospital bed. Photo: A road blocked by a landslide in Gyirong County of Xigaze Prefecture, southwest China's Tibet Autonomous Region in the wake of the massive Nepal quake.
At least 42 people were known to have died in India, including 30 in the eastern state of Bihar, while buildings in the capital New Delhi had to be evacuated. The United States Geological Survey said the shallow quake struck 77 kilometers (48 miles) northwest of Kathmandu at 0611 GMT, with walls crumbling and families racing outside their homes. The quake tore through the middle of highways in the capital and also caused damage to the country's only international airport which was briefly closed. Kari Cuelenaere, an official at the Dutch embassy, said the impact had swept the water out of a swimming pool at a Kathmandu hotel where Dutch national day was being celebrated. "It was horrible, all of a sudden all the water came up out of the pool and drenched everyone, the children started screaming," Cuelenaere told AFP. "Some parts of the city fell down, there was dust rising... There were many (rescue) helicopters." Photos: Pedestrians walk past collapsed buildings in Kathmandu, Nepal.
Aftershock tremors could be felt more than two hours after the initial quake. USGS initially measured the quake at 7.5 magnitude and later adjusted it to 7.8, with a depth of 15 kilometers. Nepal and the rest of the Himalayas are particularly prone to earthquakes because of the collision of the Indian and Eurasia plates. The thrust of the India plate beneath Eurasia generates a large amount of seismic activity, the USGS says on its website. Photo: Pedestrians walk past collapsed buildings in Kathmandu, Nepal.
A spokesman for Nepal's home ministry said the government had released around $500 million as emergency funds for rescue operations. India dispatched two military transport planes to help with the rescue and relief efforts and there were similar offers from around the region, including Sri Lanka and Pakistan. The US Agency for International Development (USAID) said a disaster response was being flown to Nepal and that the Obama administration had authorized an initial $1 million "to address immediate needs." In Europe, Britain, Germany, Norway and Spain also pledged support and assistance. Photo: People gather around a collapsed building after an earthquake in Durbar square in Kathmandu, capital of Nepal.
Chinese President Xi Jinping sent a message of condolences to his Nepalese counterpart Ram Baran Yadav and offered to provide assistance. China's official Xinhua news agency said that 13 people, including an 83-year-old woman, were killed in the Tibet region. The area has a history of earthquakes, with a 6.8 magnitude quake that hit eastern Nepal in August 1988 killing 721 people. A magnitude 8.1 quake killed 10,700 people in Nepal and eastern India in 1934. Photo: A collapsed building is seen after an earthquake in Durbar square in Kathmandu, capital of Nepal.