Himalayan Megaquake

Himalayan Megaquake

PBS Airdate: January 27, 2016

NARRATOR: An earthquake rocks Nepal. Powerful tremors catch millions by surprise.

ROGER BILHAM (Geologist): There was a very violent earthquake.

NARRATOR: Collapsing buildings kill thousands. Many are buried alive.

ANDREW OLVERA (Los Angeles County Fire Captain): And we're going to go ahead and have the rescue squad come in and help extricate that victim out of the hole.

NARRATOR: It's the biggest quake to happen here in 80 years.

MICHAEL ANDREW (Climber): Major earthquake.

ROGER BILHAM: We've never seen anything like it.

CLIMBER #1: Oh, look at that. Look at that. Look at that!

NARRATOR: The quake triggers a huge avalanche on Mount Everest, killing 20 people.

PAUL DEVANEY (Climber): Whoa, whoa, whoa! Inside!

NARRATOR: It's the Himalayan peak's most deadly day.

DAVID BREASHEARS (GlacierWorks): It looks like what you see when one of these tornadoes runs right through a place.

PAUL DEVANEY: I've never seen anything come at us like that before.

NARRATOR: Millions across Nepal are homeless.

MAN: My god!

NARRATOR: Many are cut off from the world by landslides.

SURAJ VAIDYA (Nepalese Chamber of Commerce): They've lost all the houses that they had. The whole village is wiped out.

NARRATOR: Even scientists are stunned by the powerful aftershocks.

ROGER BILHAM: Whoa! That was enormous!

MICHAEL ANDREW: Oh, my gosh. It's like the whole mountain's coming down.

MIKE SEARLE (Geologist): We've seen just one fraction of a second in a 50-million-year time interval of building the Himalayas.

NARRATOR: Can they forecast when the next big one will strike?

ROGER BILHAM: You know, it's really scary. There's no reason why one could not occur in the next 10 years or the next 10 minutes.

NARRATOR: The race is on to unravel the mysteries of the Himalayan Megaquake, right now, on NOVA.

JOST KOBUSCH (Climber): Ugh!

NARRATOR: Nepal: a nation of 28-million, among the world's poorest. In this hilly terrain, almost all arable land is used. The slopes stretch up to eight of the world's 10 highest mountains. Each spring, hundreds of mountaineers come to climb Mount Everest, the highest point on Earth. The birthplace of the Buddha, Nepal is a peaceful haven for both Buddhists and Hindus. Ancient palaces stand side by side with even older Hindu temples.

April 25th, 2015, 11:56 a.m.: The earth begins to move and doesn't let up for a full minute. There's no safe place to run.

PAUL DEVANEY: Whoa, whoa, whoa! Inside!

NARRATOR: An earthquake rips across the Himalaya,…

PAUL DEVANEY: Get down, get down, get down, get down!

CLIMBER #1: Close the door!

PAUL DEVANEY: Close the door!

NARRATOR: …unleashing an avalanche upon hundreds at Everest base camp.

PAUL DEVANEY: I've never seen anything come at us like that before. Oh, my god! Oh, my god!

JOST KOBUSCH: Are you okay?

CLIMBER #2: Yeah.

CLIMBER #3: Are you all right?

JOST KOBUSCH: Yeah.

NARRATOR: Survivors quickly become rescuers. Makeshift hospitals spring up to deal with the nearly 18,000 injured. Many are still buried alive.

Eight-year-old, Seema Tamang, was trapped under her house. She can't walk, has a head injury, but medical care is limited.

DOCTOR (Chinese Military): Here, we have no MRI scanner.

NARRATOR: There's a race to find anyone alive in the rubble.

LOK BIJAYA ADHIKARI (National Seismological Centre): This is the first major earthquake that we've experienced in our life.

NARRATOR: Since April 25th, seismometers across Nepal have recorded 400 aftershocks of Magnitude 4 or greater.

LOK BIJAYA ADHIKARI: In the first day, about 12 aftershocks were greater than five in magnitude, and they were strong enough to shake the area. This is new, for them to experience shaking every day.

NARRATOR: Over 2,000,000 are now homeless.

LOK BIJAYA ADHIKARI: There is one very strong feeling in the people that they will be hit by another large earthquake in the future, and they're scared.

NARRATOR: Shaking isn't the only threat. Over 5,000 landslides have left thousands of villages unreachable.

SURAJ VAIDYA: They're cut off from the rest of Nepal, and they've lost all their houses that they had. The whole village is wiped out. They have supplies for about 11 days. And she's not sure what she's going to do after about 11 days, but she's hoping the government will come and give some sort of a rescue, you know, drop some food up here. So living, for them, is extremely, extremely difficult, at this stage.

This used to be a cowshed, and now what you have is people actually occupying this for their shelters, yes? So you see there are four little children up here. They live up here, you see they live in the middle? That's how they're living.

NARRATOR: As the death toll rises toward 8,000, a few miracles emerge from the dust: rescuers dig a baby boy out from underneath his home on day two. Remarkably, he's unharmed.

This earthquake came without warning. People in the central mountain villages felt it first. Then, just 16 seconds later, the shaking reaches the capitol. The waves rock people like a storm at sea.

The tremors take only a minute to reach Mount Everest, a hundred and fifty miles away.

JOST KOBUSCH: The ground is shaking! Do you hear that?

NARRATOR: Irish climber, Paul Devaney, picks up his camera to record what's happening.

PAUL DEVANEY: We realized, "Wow, this is an earthquake!" And the whole of base camp is moving pretty violently.

NARRATOR: Then, up above them, the earthquake dislodges a massive block of snow and ice, which comes hurtling down, but they can't see it.

DAVID BREASHEARS: I think, probably, if it had been a clear day, people would've seen that avalanche much sooner.

NARRATOR: Photographer, David Breashears, was on the mountain that day.

DAVID BREASHEARS: They had no time, by the time they turned around.

CLIMBER 1: Oh, look at that. Look at that. Look at that. Oooh! Look, straight ahead.

Ready to go in the tents, or what?

CLIMBER 2: That is immense.

CLIMBER 1: Look, look, look, look, look! Ready to go in the tent?

NARRATOR: The climbers have a few seconds to decide where to run.

PAUL DEVANEY: I'd say, within about 50 feet of our location, a massive avalanche was bearing down on us.

JOST KOBUSCH: Oh, oh!

CLIMBER 1: Sorry, sorry.

CLIMBER 3: Look, look!

PAUL DEVANEY: Whoa, whoa, whoa, inside!

At that point in time you're just focused on, "How can I survive this?" and "Will I survive this?"

JOST KOBUSCH: Come under my jacket! Come under my jacket! Are you okay?

CLIMBER 4: Yeah, yeah, yeah.

CLIMBER 5: Are you alright?

CLIMBER 4: Yeah.

PAUL DEVANEY: I've never seen anything like that cloud come at us before. Are you okay? Are you okay?

DAVID BREASHEARS: We started to learn, three or four hours later, that there had been loss of life. Many casualties, people with serious injuries, multiple broken bones, concussions. Then, every few hours the death count went up. These were massive blunt force trauma injuries. People were blown through the air into rocks.

JOST KOBUSCH: Ugh!

NARRATOR: Ultimately, 20 people die on Everest, and in the rest of Nepal, the total dead nears 9,000. News of the devastation travels faster than the seismic waves themselves.

As the earthquake's waves ripple out, they hit seismic stations at different times. It takes 24 minutes for them to reach the other side of the earth, in Colorado, where the U.S. Geological Survey can compare the time they took to reach each station and then pinpoint where the waves started, the "epicenter."

This one started 50 miles northwest of Kathmandu.

But word travels hundreds of times faster via social media.

DR. HARLEY BENZ (National Earthquake Information Center): We monitor for the word "earthquake" in many languages. We saw a surge in Twitter traffic. Realizing it was in a heavily-populated area, an area that we know large earthquakes can do damage, I was called at home.

Within a few minutes, our seismic sensors will start seeing this earthquake, and then we'll locate the earthquake, determine its magnitude.

NARRATOR: Magnitude is the size of the earthquake at its source. This one's 7.8, sometimes called a "megaquake," an earthquake that's seven or greater.

Earthquake magnitude is not linear. The 2010 quake in Haiti, at 7.0, had the energy of 32 Hiroshima bombs. Nepal's 7.8 is more than 15 times stronger, but not as large as this highly active zone can produce.

Geologist Roger Bilham, is a first responder to most of the world's major earthquakes.

ROGER BILHAM: I immediately had a look to see how much money we had in the bank, and I purchased a ticket on the next flight to Kathmandu.

NARRATOR: He's especially interested in the Himalayan region because of its unique geologic history.

The Earth's crust consists of several tectonic plates. About 50-million years ago, one of them, the Indian plate, began colliding with Eurasia, gradually forcing it upwards, creating a massive mountain range, the Himalayas.

MIKE SEARLE: That's what builds the Himalayas. Where you have compression of two plates, the plates initially start to fold and fracture. The Himalayas is probably the largest collision that we've seen on the planet for the last 500-million years.

The Indian plate continues to converge with Tibet, at the rate of 18 millimeters a year. In some places, the plates stick, accumulating stress, which, eventually, releases all at once, in an earthquake. This is what scientists believe happened on April 25th, 2015.

MAN #1: My god!

MIKE SEARLE: We've seen just one fraction of a second in a 50-million-year time interval of building the Himalayas.

NARRATOR: This blip in the geological timeline was so powerful it wiped out thousands of villages. Rescue has been slow to arrive. A team of Nepalese athletes and nurses takes matters into their own hands. They gather tents, tarps and food to deliver to the cut off villages.

ANG TSHERING LAMA (Mountain Guide): We're going to a place called Thulo Bhotang. Maybe it's an eight-hour drive, maybe it could be 20-hours' drive. You never know.

MAN #2: Okay, bistadi, bistadi! (Slowly, slowly!)

ANG TSHERING LAMA: We are coming as a relief team. We are taking food supplies and also medical facilities. So we have Nepali nurses from New York City. So we'll put up a medical camp there.

NARRATOR: They're travelling to the district with the highest death toll, Sindhupalchok. Few vehicles have passed here since the earthquake.

UNITA MAGAR (Nurse): According to what we hear, no team, rescue team has reached there yet.

NARRATOR: They want to get food and medical supplies as far as the bus will take them. Then, they'll set up a hospital for survivors.

All homes here are abandoned.

ANG TSHERING LAMA: The villages are totally gone, but, hopefully, we can find some people and help them out.

NARRATOR: This road was just dug out from an earthquake-triggered landslide. A strong aftershock could cause another.

ANUP GURUNG (Kayaker): We are, like, around one hour away from our final destination. But this is not really looking good, but everybody believes that, you know, we will manage it. That's Nepalese spirit.

NARRATOR: They reach the village of Thulo Bhotang. Over 3,400 people have died in this district.

SUNITA BHANDARI (Nepalese American Nurses Association): I've never had a road trip like this before. So, it was quite a trip, but I'm happy we all got here, and we're all trying to do what we can do right here.

They are all traumatized and they're more scared. And they don't like trying to go in their house. There's still post-traumatic distress. We've got to talk about it, try to be strong, and then help each other, because if you don't help each other, then nobody will come and help you out.

NARRATOR: They've brought 3,000 pounds of rice and lentils to feed the villagers.

SUNITA BHANDARI: We came all the way from America to help our people. We brought all the dressing supplies, all the medication. And we're trying to help as much as we can.

NARRATOR: Seema Tamang was literally buried alive by the earthquake, pinned beneath the stones of her home for an entire day.

SUNITA BHANDARI: The kid was under the rubble for 22 hours, but the dad never gave up the hope.

NARRATOR: Unable to walk, Seema is in a lot of pain. The doctors believe she could have broken bones. An x-ray is needed, so she'll have to be evacuated to Kathmandu.

SUNITA BHANDARI: When they dig out of the rubble she, like, was unconscious, so they tried to put some water on her and she gained her consciousness. And the first thing she asked is, "How am I going to go to school now? I cannot walk anymore."

NARRATOR: Ninety-five percent of the structures in this district were destroyed, including Seema's home.

SUNITA BHANDARI: So, this is his house, he is saying. All the rocks were all piled all the way up, so they dig all the rocks out. You see all these rocks? That's from here.

PASANG TAMANG (Seema Tamang's Father): (Speaks in Nepali)

SUNITA BHANDARI: He didn't think she was alive, but, for his wife's sake, like, you know, they wanted to see, make sure, even it was a dead body, or whatever, he wanted to dig it out. And when he saw her, finally, after 20 hours, the girl said, "My left hand is in pain, Dad."

NARRATOR: But among the less lucky ones is this young woman, whose mother and baby sister died.

PRAMILA SUNAR: I live in Kathmandu. I have a job there. When my mother died in the earthquake, I came back here, and now I live in a cowshed with my brothers and sisters. One brother does not even know that mother has passed away. I haven't been able to tell him. He's only seven years old.

I can't stay here, because I don't have land here. Landslides have destroyed all the lands we had. The earthquake has rendered us homeless. Sometimes I wish I were dead, thinking that it would be better. 

This is the house. We dug mother out the day before. It was a two-story house. It went down and it became a rubble.

NARRATOR: Some of the villagers have no family left to care for them. This man was found collapsed in his home.

SUNITA BHANDARI: He's an 89-year-old male, lives by himself, and he hasn't been eating. So, today, he only drank a little bit of water. So we tried to hydrate him, we just put in an I.V.

NARRATOR: Many villagers will move away, for fear of landslides. Those who stay have nowhere else to go.

ANG TSHERING LAMA: Rebuilding the whole village again, the whole community, it's going to take a long time.

NARRATOR: Ang and the nurses have raised just enough money to call in a helicopter for Seema. A broken leg, left untreated, could be fatal. She and her father have never flown before, and this flight, through the clouds, is a risky one.

This ambulance is one of Seema's first rides in a vehicle. She's never been to Kathmandu, and now it's a city in crisis. This is a military field hospital set up by the Chinese. One of the few available x-ray machines in Nepal is here.

Surprisingly, Seema's bones are completely intact.

DOCTOR (Chinese Military): There is no fracture of bones, so maybe it's a ligament injury.

NARRATOR: The stones that were pinning down her leg may have damaged a nerve.

NURSE (Chinese Military): Are you able to move your foot? No?

NARRATOR: She can't move her toes, and without treatment she could lose the use of her leg for life.

As the aftershocks continue, everyone is afraid another large quake will strike soon. Earthquakes almost always follow patterns. These photos are from the last big one here, in 1934. It was at least an 8.0 that ruptured in an area further to the east.

Roger Bilham believes this quake is a repeat of one that happened in 1833. It ruptured in the same region with similar impact.

ROGER BILHAM: This earthquake enables us to reinterpret all historical earthquakes, and our only knowledge of these earthquakes is how people perceived them.

NARRATOR: Since there were no seismic records in 1833, Roger had to study newspaper accounts and travelers' journals. From those descriptions, he estimated the earthquake had a magnitude of 7.8, similar to the present-day quake.

ROGER BILHAM: Well, suddenly we have an earthquake that we know about numerically, which has just been felt by a million people. And those million people have spoken to reporters, and we've now been able to make a catalogue of hundreds of accounts for this earthquake. And those accounts can now be translated into a much more precise numerical evaluation of historical earthquakes.

NARRATOR: That quake was followed by a series of aftershocks over two years. But since 1833, enormous stress has built up along the fault, leading Roger to believe that the 2015 earthquake should've been larger.

ROGER BILHAM: The first thing we thought was, "Gosh, this is smaller than we expected."

NARRATOR: He expected a Magnitude 8 or higher, at least double the power of the killer that just struck.

So, how much energy is still stored in the fault? Scientists know that the plates move at 18 millimeters a year. In the 182 years since 1833, they've moved about three meters. But, in some places, the faults are stuck. And this lack of movement creates a predictable amount of strain.

John Galetzka is a geodesist who measures changes on the surface of the planet. He can tell how much of the strain the 2015 earthquake released. He's flying directly to one of the places where the two plates carrying India and Tibet are stuck.

JOHN GALETZKA (Geodesist): Thirty-three kilometers to Dunche.

NARRATOR: He'll determine just how much the locked plates, 20 kilometers below, lurched forward during the quake. If they didn't move enough, there's more stress to be released.

JOHN GALETZKA: We'll get seismic data.

NARRATOR: G.P.S. stations, fixed solidly to the earth's surface, have the answers.

JOHN GALETZKA: I'm just going to demonstrate for you how strong the monument is here. So, really, it's anchored into the earth here, about a meter and a half or two meters, glued in.

Hayaha!

NARRATOR: This is one of over 50 active G.P.S. stations placed across the Himalayan arc of Nepal, measuring minute movements of the earth.

G.P.S. satellites broadcast microwave signals to stations on the ground. The G.P.S. stations are so sensitive, they can detect shifts as small as a millimeter. Data reveals the earthquake released only half of the stress that's accumulated since 1833.

JOHN GALETZKA: This station moved to the south, about a meter and a half. So, just to demonstrate: this station was, about, right here 10 days ago, and then the earthquake happened. The earthquake happened, so: seismic waves, and then seismic waves, and the tectonic movement, the plates shifting, and then the antenna settled to where it is right now.

NARRATOR: This G.P.S. station, and others, didn't move as much as expected, because the earthquake only ruptured the lower, deeper part of the fault. This means a portion of the fault remains loaded with pent-up energy for future earthquakes.

JOHN ELLIOTT (Geophysicist): This was a very big earthquake in Nepal, but it's not the biggest that can happen. It hasn't relieved all the pressure across this large faulting area. There are other bits of the fault that still need to break, in the future.

NARRATOR: Does this mean there's more to come? This earthquake battery didn't run all the way down, it's still partially charged, leaving a reservoir of stress to be tapped by future quakes.

A bigger concern is that there are places along the fault where no stress was released by this earthquake.

Recent earthquakes have relieved built-up stress to the east, in India, and also to the west, in Pakistan. But there's an area in between, to the west of Nepal, that's locked. This earthquake didn't cause it to budge even a bit. It's a time bomb, waiting to erupt, where no movement has occurred for centuries.

MIKE SEARLE: Unfortunately, all the strain built up has not been released, and it's still down there, which means that there is some danger of further earthquakes to the west of the fault, which still remains locked, and that's a problem.

NARRATOR: Like a sleeping giant, the west of Nepal has at least 10 meters of built-up slip stored beneath it. It last slipped in 1505, that's 500 years of coiled-up potential energy, ready to spring.

ROGER BILHAM: You know, it's really scary. We know earthquakes as big as 8.6 have occurred in the Himalaya. There is no reason why one with that magnitude could not occur in the next 10 years or the next 10 minutes.

NARRATOR: The challenge is to now prepare the people for this potential catastrophe. It'll be 16 times bigger than the 2015 earthquake.

Day 5: Just as rescuers are losing hope, they discover a trapped victim still alive. Volunteers from the Los Angeles County Fire Department have arrived to help the local police.

ANDREW OLVERA: We were told that there's voices heard and a void space. We have a search reconnaissance team with us right now. And we're going to go ahead and have the rescue squad come in and help extricate that victim out of the hole.

NARRATOR: Concrete rescue saws can cut through what's left of an eight-story building. Nepal Police Force Inspector Laxman Bahadur Basnet risks his life to crawl under the tons of rubble.

LAXMAN BAHADUR BASNET (Nepal Police Force Inspector): I felt that there might be an alive victim inside the building. After calling many times, the boy responded, "Yes! Brother, I am here!"

NARRATOR: They've found a 15-year-old boy, entombed in complete darkness. They battle for five hours to free him.

LAXMAN BAHADUR BASNET: I assured him that, "We are here to rescue you. Please, you don't worry." I just make him confident that he is being rescued.

PEMBA LAMA (Earthquake Survivor): I was eating, and then the earthquake hit. When I was trying to get out, the walls broke into pieces and fell on top of me. I was unconscious at first, and then I thought it was just a nightmare.

ANDREW OLVERA: It's what we call an "entombment." So, he wasn't specifically crushed. But what he was, was inside of a box, a box with heavy concrete all around him.

NEPAL POLICE OFFICER: It's a miracle! One-hundred-forty-four hours, eating nothing and drinking nothing. It's a miracle!

LAXMAN BAHADUR BASNET: We did it! Really great job, yes!

MAN: He's a hero!

NARRATOR: Pemba Lama has emerged into a world dramatically altered. Earthquakes have the power to instantly reshape the land. Their most obvious effect is a sudden slip to one side or another. What's less obvious is that the earth can move vertically, too.

Geophysicist John Elliott figures out just how much, using satellite data.

JOHN ELLIOTT: Using this data, we can measure precisely how much the earth has moved up and down. Each of these is a contour, but instead of telling you how high the mountains are, it tells you how much higher, how much they grew or how much they reduced in size. 

Each of these is a 10-centimeter contour, we have 10 of them. And this area, beneath Kathmandu, actually uplifted by about a meter, whereas these high mountains north of Kathmandu actually went down about 70 centimeters.

NARRATOR: The earthquake caused Kathmandu to rise three feet up. Mount Everest, on the other hand, sank by about an inch.

But it was the side-to-side shaking on a ridge above base camp that triggered the avalanche. Ultimately, it killed 20 people and injured 120. But the avalanche only deposited a couple inches of snow in camp.

So what caused the death and destruction here?

DAVID BREASHEARS: This wasn't a normal avalanche. Some of these tents have thick steel poles. We later learned that when those things are hit by a 300-mile-per-hour-plus wind, they become lethal missiles.

NARRATOR: Scientists in Davos, Switzerland, simulate the physical forces behind avalanches. But they've never modelled one this extreme.

Yves Buhler and Perry Bartelt want to figure out exactly how much ice was dislodged above base camp by the earthquake. David Breashears was able to get them close-up photos of the ridgeline where the ice calved off.

DAVID BREASHEARS: I commissioned a helicopter to fly directly above base camp. And I flew back and forth with the door open.

YVES BUHLER (WSL Snow & Avalanche Research): Because David is doing so high-resolution shots, we can zoom in. So this is what we identified as the main release mass.

NARRATOR: The chunks of ice that the earthquake tremors shook off the ridge above base camp were akin to 100,000 cars plummeting toward camp.

The avalanche took 60 seconds to descend nearly 3,000 feet, reaching speeds of up to 157 miles an hour. The impact of the ice mass hitting ground zero detonated a force comparable to a bomb blast.

PERRY BARTELT (WSL Snow & Avalanche Research): One powder cloud jet managed to push its way through, and it shot it directly towards the base camp.

NARRATOR: Upon impact, the avalanche kicks up an envelope, called a "powder cloud," one percent snow and 99 percent air.

YVES BUHLER: And that's what we observed in the video, that it was, like, ejected into the air.

NARRATOR: This powder cloud reached a height of 650 feet. And, just in front of that cloud blasts an invisible, but deadly, pressure wave.

The Swiss team determined that the force of the pressure wave, indicated here in red, was enough to flatten a wooden building. Many climbers were killed by a violent blast of air moving at more than 100 miles per hour.

YVES BUHLER: The color is the pressure, so, the pressure that people experienced when they were there. And red means the limit where a person gets smashed against rocks.

NARRATOR: Climber Paul Devaney photographed huge barrels that were blown from the camp, several hundred meters, across the glacier, into a gully.

PAUL DEVANEY: It's a scene of pretty surreal devastation. It's just like a plane crash or something. It's hard to imagine what's just happened here in the last few hours.

NARRATOR: At the same moment, nearly 100 miles away, a similar, and even more deadly avalanche hit the village of Langtang. David Breashears photomapped the devastation.

DAVID BREASHEARS: When I flew in that helicopter up that valley and over Langtang, I really had a hard time getting my head around what I was seeing. An entire village was gone, obliterated. Thousands of trees, trees this big around, were flattened, stripped of their bark and branches. It looked like what we had seen after the volcanic eruption of Mount St. Helens.

NARRATOR: David stood at the place where he had taken a photo of Langtang in 2012 and shot an exact match.

Over 400 people and 116 homes were lost in an instant. How could such a colossal event come to pass, without a trace of warning for those below?

PEOPLE YELLING: Fast, fast! Quick, quick!

NARRATOR: In the village above Langtang, a similar event occurred.

DAVID BREASHEARS: This would've been a group of people who would've gotten out of their buildings and said, "It's okay." And then they would have no idea what was coming from 10,000 feet above them.

NARRATOR: They had survived an earthquake, but out of the clouds came something even more powerful.

KYANGIN GOMPA (Trekker): Look, look, look!

KAT HELDMAN: Oh, my god!

NARRATOR: The earthquake unleashed multiple avalanches onto Langtang valley, one of the most popular trekking routes in Nepal.

PERRY BARTELT: It took the avalanche about 80 seconds, after release, to get down to the valley bottom. And the avalanche reaches tremendous speeds and shot out, almost directly, into the air above Langtang, and then plummeted into the valley bottom.

NARRATOR: People just below Langtang, in the narrow valley, suffered from pummeling rocks and debris.

MAN #1: Here comes more!

NARRATOR: The cloud could be seen for miles. Everyone was running from plummeting boulders and landslides.

AUSTIN LORD (Anthropologist): And it was breaking everywhere, and it was breaking in places you couldn't see, and it was in the clouds. And you could hear it coming from 2,000, 3,000 meters above.

NARRATOR: Austin Lord captured this footage in a village two miles below Langtang.

AUSTIN LORD: You weren't sure if all of a sudden something would burst through the clouds that you couldn't run from.

MAN #1: Here comes another tremor!

AUSTIN LORD: Splinters coming from the sky, small rock debris coming from the sky.

PERRY BARTELT: The houses that were directly in the path of the core had absolutely no chance. They were demolished and blown away immediately.

DAVID BREASHEARS: It looks like what you see when one of these tornadoes of epic proportion just runs right through a place.

NARRATOR: This was a mega-avalanche. A chunk of ice, larger than the Empire State Building, fell three times farther than the Everest avalanche, more than 10,000 vertical feet, reaching a speed of 225 miles per hour, before hitting the village of Langtang.

PERRY BARTELT: That would be 10-times the most extreme avalanche we would have in Switzerland. And that's just a very, very extreme and unique avalanche event.

NARRATOR: Austin Lord was among 300 survivors stranded in Langtang Valley, unable to get out, due to landslides and avalanches blocking the way.

AUSTIN LORD: And then I looked upslope, where Langtang should've been, and you could see that Langtang was just gone. And I was standing with two or three other people who realized it at the same time as me, locals whose families are located above, and below, and in Langtang, and it was heart-stopping.

Local people were seeing each other, realizing who was gone, who was still there, people coming down saying to the people coming up: "There's no one. This is, this is everyone." And just people collapsing, just people breaking and melting and children wailing. That was the hardest part.

DAVID BREASHEARS: We were wandering down this trail, with debris on both sides of us, and we saw a man coming up the trail towards us. And he'd come back up the valley, having evacuated it, to look for his wife. And along with the army search team he had found her body 10 minutes earlier.

The earth shook. Ten thousand feet above him, the ice fell, and in the blink of an eye his life had changed. He had no home, he had no wife, and he had only the 600 rupees in his pocket, and that was six dollars. And that's something that I will never forget.

NEPALESE MINISTER IN PARLIAMENT: (Speaking in Nepali)

NARRATOR: Seventeen days after the mainshock, huge tremors rock Nepal again.

Cameras in Parliament capture the panic.

ROGER BILHAM: About a minute ago there was a very violent earthquake. We don't know where it was, probably about 20 or 30 kilometers from Kathmandu. And it set the whole valley shaking, just like it did in the main earthquake. Everyone was absolutely terrified!

NARRATOR: Could this be a big aftershock, as in 1833? Or the big one from the west of Nepal that they've been dreading? Rarely does a seismologist get to be part of an earthquake he is studying.

ROGER BILHAM: I think it's still moving!

PATRICK GREAVES (Producer): It is still moving.

ROGER BILHAM: Good grief!

To see people with their arms outstretched, wondering what was going to hit them, even though there was nothing above them. Only trees and birds. People don't do that unless they've just recovered from an even worse shock, which of course was 16 days ago, the mainshock.

This is what happened in 1833. About two weeks later, there was a large aftershock that was felt in India. And I'm sure this one would have been, too.

NARRATOR: Roger will be able to determine if it's an aftershock or a new earthquake in a matter of minutes.

ROGER BILHAM: I've dialed up the U.S.G.S. earthquake page, and I'm sitting here waiting for a dot to appear on the map to tell me how big and exactly where it was.

It takes 24 minutes for a seismic wave to cross from one side of the Earth to the other. And what we're waiting for are the seismic waves to hit those distant seismometers and then for their data to be transmitted, via satellite, at the speed of light.

(To taxi driver) Keep going for 1.5 kilometers. Yeah, go down here.

And these data arrive in Golden, Colorado, and then they're processed to find out how big and exactly where and how deep the earthquake was.

NARRATOR: The shaking is intense enough to send people running out of buildings. Bodies of water sloshed in waves.

ROGER BILHAM: Whoa! That was enormous! It's a 7.4. My goodness! So, this is only a little bit smaller than the mainshock. No wonder people were scared. The mainshock was 7.8. This was 7.4, which means the energy released is four times less, but to the terrified inhabitants of this city, the impact was just the same.

It was 83 kilometers from Kathmandu. It was near Mount Everest. So that will have produced an enormous amount of avalanches. It's really tragic.

NARRATOR: Roger concludes it's an aftershock, to the east of the mainshock, a section of the fault that hadn't moved enough and was catching up, releasing as much energy as a 25-megaton bomb.

ROGER BILHAM: This aftershock was big enough to be a mainshock in its own right.

Let's go and talk to the survey department. It was Magnitude 7.4!

NARRATOR: When an earthquake strikes, scientists need to know not only the magnitude at the epicenter, but also the intensity of the shaking felt in each village.

Roger and David Breashears fly over the region.

DAVID BREASHEARS: Roger's mission was, by looking at buildings and the way that they had held up, he could determine the shake intensity. It's the velocity at what the surface of the earth was moving at and the frequency.

There were no instruments in these mountain areas to measure the shake intensity, but Roger knows how to determine that by what happened to buildings.

ROGER BILHAM: We needed to get out here quickly, because in the days following an earthquake, people already start cleaning up. You don't leave a pile of rubble in your front yard. So, we lose some of the clues that we need, to understand why the buildings fell down.

NARRATOR: They maneuver close to villages so David can shoot high-resolution photos.

DAVID BREASHEARS: We'll be able to zoom in on those images and even look at such fine detail that you can just see bricks or stacked fieldstone, and from that, Roger was able to make a determination.

NARRATOR: Using a shake intensity scale, Roger puts a value, between one and 10, on the observable damage produced in each village. If crockery falls off a shelf, it's intensity six; poorly-made buildings will partially collapse at seven, but they'll flatten at eight; total destruction would result from intensity 10.

This scale informs engineers rebuilding for the next big quake. Over 770,000 buildings were either damaged or flattened by this earthquake.

Why did some collapse and others survive? There's a clue in the heart of Kathmandu. Durbar Square experienced intensity-7 shaking. It's a World Heritage site turned to rubble. But the dust-laden debris, dating back to the sixth century, holds a secret.

KAI WEISE (Consulting Architect for United Nations Educational, Scientific and Cultural Organization [UNESCO]): The big earthquakes only come every 80 to 100 years, so there's a generation gap, very often, and then they have to relearn the need to protect themselves. After the last earthquake, I mean, we were still reconstructing after 80 years.

Initially, it was just a shock to see on the news all these images, and it's just unbelievable. But then it slowly sinks in and you sort of have to accept the fact, you know, what kind of destruction there has been.

NARRATOR: Coronations of kings have taken place here: five acres and 10 courtyards, dominated by the white 19th-century portion of the neoclassical Hanuman Dhoka palace, the newer wing of the original palace, built in the 1770s. The palace presides over some of Kathmandu's oldest living temples.

KAI WEISE: Most of these temples are still being used, and they have religious value as well as purely cultural value.

NARRATOR: This undated stone image of Kal Bhairav, the Hindu god of justice, has survived many quakes.

KAI WEISE: Out here, we see that two of these tiered temples, on these platforms, have totally collapsed. Very clearly, these two temples sort of create this whole space here, which is a part of the identity of the city.

They went in with heavy machinery to clear it up, and the problem is heavy machinery impacts all of the material that could be reused later on. But we've tried to salvage as much of this material as possible.

There are all these different elements, and I think they have been mixed up between the temples. And that will be a major challenge, just trying to figure out where these different elements came from.

NARRATOR: Damage assessment of heritage buildings requires detective work. The skin of a centuries-old palace can hide the true structure within. Why is the old palace still intact, while the newer, white palace walls must be shored up?

KAI WIESE: So, we were scared that that would actually collapse, and if it would, it would bring that whole corner down.

NARRATOR: The white plaster-faced building is failing. Both are brick construction and have suffered through past earthquakes.

Randolph Langenbach is a conservation architect. He travels to earthquake zones to find out what makes some traditional buildings earthquake-resistant.

SARASWATI SINGH: Mind your head.

NARRATOR: Randolph finds timber hidden within the brick facade.

RANDOLPH LANGENBACH (Conservation Architect): It's not just a single timber, but it essentially is like placing a ladder onto the wall, in other words, this cross piece is very much a part of the system.

KAI WIESE: So, you have the beams on the inside and outside, and then it's held together with this one, which goes through, so that it basically ties the wall together.

RANDOLPH LANGENBACH: You know what's interesting? You know what I realized? It's a frame, timber-frame structure.

KAI WIESE: Yeah, yeah, yeah. You can see the woodwork going all the way through the ground floor. And in one corner, probably one of…

RANDOLPH LANGENBACH: Vertical woodwork.

KAI WIESE: Yes, yes, yes! And it's tied together.

RANDOLPH LANGENBACH: Then it answers the question. It answers why it behaved. It had a different sympathetic motion. Because this is a frame structure, it's actually more flexible. And it's rocking back and forth, essentially, as a solid unit, so it can't travel with this. And it broke everything up around it, but it stayed intact.

NARRATOR: It's the timbers hidden within the brick masonry that laces the older palace together, holding it firm, yet elastic enough to withstand an earthquake.

KAI WIESE: So, here, the beautiful thing is that they also started to put in ornamentation within the latticework. Up here, you can see these beams. They're tied with the wooden pegs. And now that is to hold the brickwork. This is really traditional earthquake technology.

NARRATOR: This combination of timber-lacing with brick was not used in the more recently-constructed white palace, which is on the verge of collapse.

KAI WIESE: They had to develop this system of combining the wood with the brick work. And it took centuries for them to develop this. And it became the traditional system of construction, but then, later on, they forgot these lessons.

NARRATOR: For the 2,000,000 Nepalis faced with rebuilding their homes, this critical lesson in protecting themselves must be relearned. But wood in remote villages is often not available, so how can the millions who live in fieldstone villages build earthquake-resistant homes?

ROGER BILHAM: The village construction practices have to use indigenous materials. They don't have access to cement, bricks are not available. Instead, they use local stones, and they do not adhere to the cement that they have to use, which is mud. And mud is incredibly weak.

Some of the structures that survived have wooden tie beams around the walls that have held them together.

NARRATOR: One of the hardest-hit districts, close to the epicenter, is Dhading.

Randolph is on a mission to rebuild a home that is earthquake-resistant, using local materials. The right consistency of mud, hardware wire and stone is all that's needed for a safe home, made in the traditional style for much of Nepal. The wire was purchased at the nearest hardware store and carried in.

RANDOLPH LANGENBACH: One thing they had was wire fencing for keeping the animals in. The idea came to my mind, "Well, why not use the wire?"

NARRATOR: Randolph's idea is to install a reinforcing element he calls "gabion bands" right into the masonry walls, just like the Hanuman Dhoka Palace. Gabion is a wire cage filled with rocks.

DIPENDRA GAUTAM (Structural Engineer): We need 22 feet.

NARRATOR: Structural engineer Dipendra Gautam trains local stonemasons to use gabion bands as a substitute for timber bands.

DIPENDRA GAUTAM: We are trying to promote some local construction technology, low cost, so definitely this is the better option.

NARRATOR: The homes in this region suffered intense damage. Ninety percent have to be rebuilt. Add a simple band that ties the walls together, even with bicycle tubes, and the building might hold.

RANDOLPH LANGENBACH: They needed to have some tensile reinforcement in the walls, and the traditional way of doing that was in the series of bands.

NARRATOR: Each wire band has a layer of stone and mud mortar placed onto it. This is wrapped into a cage and all four walls of the building are tied together to form what engineers call a "ring beam."

RANDOLPH LANGENBACH: The band seemed to be something that could be hand-carried in. It could be understood by people in a short explanation.

NARRATOR: This will be home for a man named Ram, who is a Dalit, the lowest caste in Nepal. His father committed suicide last year, and the earthquake then destroyed Ram's home.

DIPENDRA GAUTAM: I think this is a very happy moment in his life, because he has earned something. This is the most satisfactory day in an engineer's life, in a conservation architect's life, because a guy who was really helpless has got a home.

RANDOLPH LANGENBACH: The timber-lacing that we saw in the 18th century part of the Hanuman Dhoka palace—and those parts have survived almost entirely intact—is a way of giving tensile strength to the wall. And this is a basic engineering concept. This is not distant at all from what engineers say is needed.

NARRATOR: We know another earthquake will come, maybe in two years, as an aftershock, or maybe the big one will rupture from the west of Nepal, but Ram is now better prepared.

This earthquake took nearly 9,000 lives, but Seema Tamang, who was buried under the rubble of her home for 24 hours, survived the odds.

DR. BRUCE GARDNER (Physician): How do you feel today?

SATISH MANPATI: (Translated from Nepali) How do you feel today?

NARRATOR: She had little hope of recovering the use of her leg, but she wants to go back to school, and get there on her own two feet.

Having lived through a megaquake, the first of their lifetimes, are the people of Nepal now more prepared to face their seismic future?

ROGER BILHAM: This earthquake acted as a kind of a Rosetta Stone, interpreting all previous earthquakes. And I'm sure we are going to see enormous headway as a result of this earthquake. Not only from the seismological point of view, but from the philanthropic point of view, and earthquake engineering, and what kind of buildings we need to survive the next earthquake.

NARRATOR: The pent-up tectonic stress, miles beneath the Himalayas, continues to build.

BRUCE GARDNER: Can you lift your toe? This one? And now this one. Straighten the good one. Straight. Oh, look at that! They both go straight. So that means this quadriceps muscle is working, which is good.

NARRATOR: Living with large earthquakes is a reality for the people of the Himalaya, since they happen in Nepal about every hundred years.

JOHN GALETZKA: Thankfully, the earthquake wasn't that big. Tragic, yes. But, let's see if we can't learn now, from this earthquake, to help us get prepared for that next big one, whenever it comes.

BRUCE GARDNER: This is fantastic! Come back here, Sweetie. I'm so happy for you. This is great. This is really good.

NARRATOR: Nepal is a nation that will walk again, because this earthquake not only tells a story about the past, but about the inevitable seismic perils that will come in the future.