Located on a major faultline dividing the Indian and Eurasian plates, quake-prone Nepal is set to suffer more aftershocks in the coming months, some of which might be major, experts say.
Here are answers to some key questions that have emerged since the quake on Saturday, April 25 that killed over 2,500 people.
What caused the earthquake?
The massive 7.8-magnitude earthquake - the worst disaster to hit the Himalayan nation in more than 80 years - occurred when a major fault broke, generating powerful seismic waves for about 100 seconds.
The colossal fault jerked after decades of pressure pushed shifting tectonic plates into a collision.
The rupture began north-west of Kathmandu and spread eastwards over a distance of some 100km.
The quake resulted from a collision between the Indian and Eurasian seismic plates, according to the United States Geological Survey (USGS).
Jerome Vergne, a seismologist at the School and Observatory of Earth Sciences in Strasbourg, agreed. "The Indian plate rises at a speed of some 2cm a year... and it is constantly trying to climb under the Tibetan plateau," he said.
"But that shift isn't smooth: it is very irregular. What happened here was a major jolt, a brutal rupture in the interface of the fault that separates the two plates," he added.
What should we expect in the days and months to come?
Aftershocks are expected in the months, even years ahead. The rupture was not homogenous, and new jolts, however small, may still bring new quakes.
"To start with, the surface (of the fault) south of Kathmandu did not break," said Pascal Bernard of the Institute of Earth Physics of Paris.
The partial break may mean the area has become even more vulnerable to new quakes in coming years, he said.
Aftershocks will continue, decreasing in number and intensity over time.
"We have observed aftershocks so strong their magnitude nearly matched the initial quake's," said Vergne, referring to the 6.7-magnitude aftershock on Sunday, April 26.
The impact of aftershocks, he added, has been worsened by the fact that structures were already weakened by the first quake.
The jolts will eventually slow down, but the plates will never stop shifting, causing new dangers as they move.
Should we fear an even bigger quake?
This convergence of continents - which created the Himalayas to begin with - has made the area one of the world's most quake-prone, with its colossal faults jammed close together.
"We know there will be new major earthquakes in the Himalayan area, which could have an even bigger magnitude than this one," Bernard said.
"Imagine yourself stretching an elastic band: it will snap in the end," he added.
A magnitude 8.1 quake killed 10,700 people in Nepal and India in 1934. A previous mega-quake in the area dates back to 1255.
Bernard said the next quake could have a magnitude of up to 9, but that it is hard to tell whether it will strike in a few years' time, or two centuries from now.
"Yes, the worst is yet to come, but it may be in a few centuries' time," he said.
How many people were affected?
The United Nations has said that more than 6 million people live in the areas of Nepal that have been affected by the earthquake. Many individuals have either lost their homes or have been forced to live on the streets because of the threat of further aftershocks.
Gary Shaye, director of humanitarian operations for Save the Children who worked in Nepal in the 1970 and 1980, said: “What’s important to remember about Kathmandu is that it’s densely, densely packed.”
He added: “This is a village that grew into a city... There is not a lot of open space to accommodate people who get displaced.”
The UN Children’s Fund (Unicef) estimates that at least 940,000 children have been severely affected in the area which includes Dhading, Gorkha, Rasuwa, Sindhupalchowk and Kathmandu districts. “This crisis leaves children particularly vulnerable - limited access to safe water and sanitation will put children at great risk from waterborne diseases, while some children may have become separated from their families,” Unicef said.
Can the hospitals in Nepal cope with the disaster?
The earthquake has exposed the woeful state of Nepal's medical facilities as hospitals struggle to treat vast numbers of injured with limited supplies and staff. The country of 28 million has only 2.1 physicians and 50 hospital beds for every 10,000 people, according to a 2011 World Health Organisation report.
So far many of the seriously injured in Kathmandu were being referred to Bir Hospital's Trauma Centre, which opened in February this year with 200 beds. Doctors said they needed more than 1,000 more beds to treat the patients that were being brought in ambulances and taxis.
Children with multiple injuries were laid on the dusty marble floors of the hospital, while hundreds of other patients with fractured and bloodied limbs lay on the ground outside the hospital under tents, as family members struggled to find drinking water and food for them.
A lack of morgue facilities meant that 13 bodies lay outside the hospital, one of the oldest in Nepal. Many patients were prematurely discharged to accommodate the waves of injured survivors: Doctors shifted wheel-chair bound patients and several quake survivors with multiple injuries to a playground opposite the hospital.
What challenges do aid agencies face?
International aid agencies and governments mobilised to respond said they faced challenges in getting assistance to the country and distributing it amid the widespread devastation there. Development workers said that continued aftershocks, a crippled transport network and the loss of power in parts of the country had made it tough to search for survivors and distribute much-needed supplies.
And employees of aid organisations have been affected themselves even as they organise responses to the catastrophe. Sanjay Karki, country director for Mercy Corps, an international aid organisation, said some members of his staff had lost their homes and that although his own house was still standing, his extended family in Kathmandu was camping outside until the aftershocks subsided.
Experts said remote areas, some of which are reachable only on foot, may have to wait longer to receive help. Nepal’s poor road network, a limited number of helicopters and planes to shuttle supplies to distant villages, and intermittent communications throughout the country, would likely worsen the current situation, they said.
“People can’t get blankets, cooking equipment and other supplies in rural villages,” said Hodgson of Save the Children. “The problem is getting that type of kit on the ground.”
While Kathmandu’s airport remains open, disaster-relief experts said that less than a fifth of the regular daily flights were now arriving, as airlines were concerned about the effect of aftershocks.
“Hospitals were trying to accommodate a huge influx of patients, some with amputated limbs, and were running short of supplies like bandages and trauma kits,” Jamie McGoldrick, the UN resident coordinator in Nepal, said. “Water supplies, a problem under normal circumstances in this fast-growing city, will almost certainly run short,” he added.
What is the estimated cost of reconstruction?
Rajiv Biswas, Asia Pacific chief economist at business research firm IHS, said long-term reconstruction costs in Nepal using proper building standards for an earthquake zone could be more than US$5 billion (S$6.6 billion), or around 20 per cent of the country's Gross Domestic Product.
"With housing construction standards in Nepal being extremely low... the impact of the earthquake has been devastating based on initial reports," he said in an early analysis of the likely damage.
SOURCE: AFP, REUTERS, NEW YORK TIMES