The initial USGS shake map of the Nepal earthquake predicted extreme shaking in Kathmandu because of the local--seismic wave amplifying--geology of the Kathmandu basin. They later revised this to reflect the lesser, but still very strong shaking that actually occurred.
Sunil Sharma/Xinhua Press/Corbis
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.
Pratap Thapa/Xinhua Press/Corbis
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.
Chen Tianhu/Xinhua Press/Corbis
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.MORE: Hundreds Dead After Massive Earthquake Hits Nepal
Terrible as Saturday's earthquake was in Kathmandu, geologists fear more bad news to come as information filters in from the surrounding mountainous countryside which has been cut off from the world by the disaster.
Landslides are certain to have blocked roads and rivers, caused flooding, and may have tumbled entire communities off mountainsides.
“It was the same with the Kashmir earthquake in 2005,” said landslide researcher David Petley of the University of East Anglia in the UK, and author of The Landslide Blog. “Saturday morning, utter chaos. In that case the death toll took a huge jump on Monday when it became clear how badly affected the mountains were.”
The mountains north of Kathmandu are heavily populated, with terraced fields and villages on very steep, landslide-prone slopes.
"The impact of the earthquake in these regions is going to be dreadful," Petley wrote in his blog on Sunday, in which he also detailed some estimates other researchers have done to quickly assess the landslide.
He also points out that there has been a lot of confusion about the area affected by the main magnitude 7.8 event. When the U.S. Geological Survey posted its initial maps of Saturday's earthquake, it featured something rarely seen: a smudge of scarlet indicating the highest, most violent shaking on their scale.
If that was not awful enough, the smudge had swallowed up Nepal's capital, Kathmandu. But the map also had a star indicating that the epicenter of the quake was 50 miles (80 km) to the west of Kathmandu and far from the red smudge.
So why was the worst shaking in and around the city?
The answer lies partly in how the Earth ruptured to make the quake. In this case the epicenter on the map marks where the rupture started, explained geologist and Himalaya researcher Roger Bilham of the University of Colorado. From there the rupture unzipped eastward for 75 miles – right under Kathmandu and beyond.
The fault that this happened along is a lot like those that have created historic mega-quakes in Sumatra, Japan, Chile and Alaska. All are subduction zones, where one plate in Earth's crust is being forced under another. This makes for faults – or "detachments" as they are called – that allow blocks of crust and wedges of material to slide atop one another.
But unlike in those other major big-quake makers, the actual Himalaya collision zone is not deep underwater. "It is inhabited by millions of people," said Bilham. "Nearly everyone in Nepal lives 5 to 10 km from the detachment."
Said another way, all Nepalis live right on top of the detachment, which is deeper in some places than others. That's also why aftershocks are still happening throughout the long rupture zone, including a magnitude 6.6 quake to the east of Kathmandu on Sunday – on the far eastern end of the rupture.
The Nepal quake affected climbers on Mount Everest, killing 18, and trapping others at upper base camps on the mountain.STRINGER/NEPAL/Reuters/Corbis
"All the aftershocks are just surrounding Kathmandu," said Bilham. "It's a terrible thing and almost a worst case scenario for Kathmandu."
The other reason the shaking was expected to be worse in Kathmandu than at the epicenter is that the city was built on the bed of an ancient lake. Like most lakes, it filled up with a lot of sand, silt and other soft sediments that were left behind then the lake drained away. Such sediments are known to amplify seismic waves and even liquefy during strong shaking.
The good news, however, is that the USGS backed away from the red smudge as the picture on the ground became clearer. The main shock appears to not have shaken Kathmandu as violently as initially predicted, said Bilham. Backing that up are reports of some fragile buildings that should not have survived are still standing, he said, and that the death toll in the city is not as great as had been feared and predicted by geologists over the years -- which was tens of thousands of deaths.
“It's kind of good news," observed Bilham, "but how much good news is there when the capital of a poor nation is hit like this...."
Petley is also holding out hope that the small bit of good news extends to the areas beyond Kathmandu.
"I am hoping that somehow Nepal has dodged a bullet," Petley said. "Time will tell."
How to Help
The site Charity Navigator lists seven vetted relief groups that are assisting in aid and recovery efforts. These agencies will be providing food, shelter, medicine, clothing and hygiene items. All received a 3 or 4-star rating from Charity Navigator:
Catholic Relief Services
Save the Children
Freelance science writer Larry O'Hanlon also manages the AGU Blogosphere, which features The Landslide Blog.