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Japan Tsunami -

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(generated from captions) on an extraordinary scale. It was tragedy the earth off its axis. A quake so powerful it knocked Tens of thousands dead, 3m out to sea. the whole of Japan shifted dropped over a metre. Parts of the coast together to create What were the forces that came this horrifying disaster. is investigating. A team of scientists a such a surplus of data. Never before have we had in this earthquake, There are no mysteries we know exactly what happened. Japan's coast lies in ruins. even worse. Incredibly, it could've been of how science saved lives, This is the untold story together exactly what happened. and how scientists are piecing leading earthquake expert. Professor Roger Bilham is a world He's in Japan to witness the immediate aftermath. the coast right now So we're flying right over about a metre. and much of the coast has sunk is truly amazing. The extent of the damage in its path. The tsunami picked up everything tumbled them relentlessly inland Cars, houses, warehouses, and just on and on and on. exactly how far it went, One of the things I'd like to see is on these gigantic tsunamis. what kind of debris gets left behind to conduct an aerial survey Bilham is the first geologist of the damage. has been recorded by seismometers, Every detail of the disaster strain gauges and tidal gauges what happened. allowing experts to analyse exactly a human tragedy But this was first and foremost on an unimaginable scale. infrastructure. It ripped away much of Japan's nations brought to its knees. One of the world's most developed pick through the debris, As rescue workers the world take on the challenge Bilham and other scientists around the massive earthquake of understanding such loss of life. in the hope of one day avoiding 100 kilometres off the coast. The source of the disaster lay the earth was distorting. Beneath six kilometres of water, A vast, slow motion collision. The earth's crust is made up of of rock. several continent-sized slabs Tectonic plates. these plates. Japan lies on a boundary between at eight centimetres a year, The Pacific plate is ramming into it grow. about the same speed your fingernails it, snagging and catching as it goes. The Pacific plate drives underneath The plate that Japan sits on under the strain. compresses and buckles immense stresses build up. Over decades and centuries, earthquake The energy that drove this for a couple of hundred years. had been building up Pacific plate It's caused by the movement of the towards the Eurasian plate. that's being wound up for 200 years. Think of it as a giant elastic band at 2:46pm Japanese time, On March 11, 2011, the stresses reach breaking point. earthquake this size is really huge The amount of energy released in an in large units. and you have to measure it that devastated Hiroshima, If you take the atomic bomb two million of those. this event was probably A really huge amount of energy. Shockwaves radiated out. The fastest, known as P waves, travelled at six kilometres a second. up instantly. Japan's detection systems pick them what was going on, Within seconds before anyone realised across the country. automatic warnings flashed A computer generated announcement parliament broadcast. even interrupted a Japanese kicked in, By the time the warning system the coastal city of Sendai, earthquake originated, was shaking. just 130 kilometres from where the shockwaves called S waves The slower, but more destructive had now arrived. kilometres a second. These waves travel at three into chaos. They threw north-east Japan As the shockwaves raced outward, of the epicentre, 150 kilometres south-west they slammed past Fukushima Dai-Ichi, housing six reactors an aging nuclear power station electricity for the local grid. and generating 4.5 gigawatts of near the reactor This footage from a town of the earthquake's power. gives some idea automatically shut down the reactors, Japan's warning system had cooling them would take time. When you think shut down, because it's shut down. you think the danger's gone was still extremely hot. But the reactor core oven and you shut the oven off, You know, if you have a pan in the even after you've turned it off. that oven continues to heat inside generators kicked in After shutdown, emergency diesel through the reactor cores. to pump coolant the earthquake intact, Fukushima survived but there was one big problem, it stands just metres from the sea. Tsunami Warning Center in Hawaii, 11,000 kilometres away, the Pacific staff got emergency pager messages. the earthquake starting, Within ten seconds of monitored around the world. its effects were already being there was a lot of information fast. Japan has lots of seismometers so when we got our page. So the earthquake was still going on a magnitude of around seven. First indications, the figures started to climb. But as data flooded in 7.5. 7.7. Up into the eights. was, 'That's not right.' The immediate reaction of everybody Because in the history of Japan an earthquake larger than 8.4. there has never been what we were doing Really heightened the intensity of something very big because we knew we were dealing with the whole Pacific basin. and something that could affect We realised, 'Oh, this is it,' 'This is horrible for Japan.' and then immediately you realise, slipped. 100 seconds since the fault line destructive S waves reach Tokyo. The slowest-moving but most (Man speaks Japanese) Tokyo was already braced, With 60 seconds warning, but not for this. five minutes. The quake lasted an unprecedented was in the city that day. One American geologist 20 seconds, something like that, We expected it to end after 10, 15, maybe a minute at the most. About minute three or four, we were just all kind of astonished that it just kept going and going and going. What is different about a big earthquake is that it begins but it doesn't stop. We were just looking at each other going, 'Is this over yet?' 'No, it's not, it's still going.' It was kind of a growing realisation that it was just getting bigger and bigger and bigger and it had to be fairly close. In a nearby park an American tourist found the ground opening up at his feet. No-one has ever filmed this happening before. The footage reveals a characteristic of earthquakes - liquefaction. As the ground is compressed, water is squeezed and forced to the surface. OK, we have an earthquake right now. And this is actually moving. Can you see the cracks moving? That crack was not there. The crack is getting bigger and smaller, going back and forth, and there is water coming up all over in the park right now. OK, here's a huge crack, and it's still moving. It's just going back and forth, swaying. It's making me kind of nervous. This land could just go, potentially, I don't know. In the days to come, scientists would regrade this quake as a magnitude 9. The warning systems worked and most buildings were still standing. But even before the quake had finished, everyone in Japan knew worse was to come. There were only minutes before a tsunami would arrive. The question now was how many would escape in time. The tsunami was triggered by the explosive energy release of the earthquake 100 kilometres off the coast. What caused it? Over centuries, the Japanese side of the tectonic fault line had been compressed and dragged downwards by the Pacific plate driving beneath it. The whole upper plate behaves basically like a rubber block. It just compresses like a spring like this, and when the earthquake happens, it springs back. The sudden upward flip of such a huge slab of rock lifted a six-kilometre deep mass of water upwards to the surface of the sea. As it collapsed back, immense waves raced out across the ocean. Not like normal sea waves, more like shockwaves from an explosion. Just a metre high, but over 100 kilometres from front to back and travelling at terrifying speed. The energy heaved up the sea floor, that displaced a vast amount of water that we can see, made its on land, it made its way off around the Pacific. One side of the wave hurtled out across the Pacific, the other side raced towards the coast of Japan. Tsunamis travel very fast at a speed that depends on the water depth. And because in the deep ocean a tsunami travels very fast, reaching at times the speed of a jet aircraft. At over 800 kilometres per hour, the wave took just minutes to reach the coast. Here, the shallower sea floor slowed down the front of the wave. The wave's fast-moving rear was still racing in. It began to catch up with the front. The increasing pressure pushed the seawater up into a rising swell. Five kilometres out to sea, a coastguard crew captured this extraordinary footage. The tsunami rearing up as the water beneath it grew shallower. Then, when they crested the first wave, a second loomed behind. The swell became a breaking wave as the rear of the wave continues to pile in, sucking in the sea ahead of it. The very thing that seems to have happened is that the sea left the land and some of the footage we've seen shows a huge shoreline being exposed and then the tsunami built up offshore and the dynamics of the wave carried it inland. Probably a cubic kilometre of water just sploshed landward and kept going until it ran out of steam. These remarkable pictures caught the moment when the sea pulled back as the first wave roared in. The tsunami had arrived. The wave's effect was strangely unpredictable. At first glance it seemed there was no discernible pattern to where it struck and when. First came Ofunato in the north. Then Sendai to the south. And Miyako in the north again. Measurements from tsunami monitoring stations along the coast were equally puzzling. The height of the wave varied dramatically from town to town. But why? The varying depth of the seabed was partly to blame. Where the water was deeper, the tsunami travelled faster and reached land more quickly. Another factor is the complex detail of cliffs, bays and inlets along the shoreline. It boils down to how the wave is focused and defocused by the geography or the topography of the coastline itself. This is Ofunato where the wave hit first. Deep water off the coast offered little resistance to the wave. Tsunami warnings did sound, but here there was little time to get to higher ground. The best early warning system people would've had would've been the fact that there was an earthquake. People have got used to the fact that if you have an earthquake, there is a possibility of a tsunami that will follow. But in the timescale they had, there was very little time or very little opportunity for escape. The tsunami hit Ofunato just 20 minutes after the earthquake. Water that actually hit the coast will be well in excess of a billion, probably ten billion tonnes of water. That's a little bit like taking a million swimming pools and emptying them onto the coastal areas of north-east Japan. 15 minutes later, the tsunami hit Sendai, 116 kilometres south. The area around the city is mostly farmland, low-lying, fertile and flat. That's why the tsunami barely slowed as it smashed ashore. The flat land was perfect for an airport too. It opened just four years ago. A kilometre from the coast, it was deluged. (Terrified cries) It hits very low-lying areas, there's nothing to stop it moving inland and so it can move inland six, seven kilometres without being impeded. There's not much to slow it down and because the wavelength of the tsunami is so big it's not going to stop until it reaches something, reaches some sort of high ground and it will just keep on coming. Next to be hit was the Miyako coast 180 kilometres back to the north. What happened here highlights another mystery. The area had good tsunami defences, the residents were prepared. They should've been safe. Last time a tsunami hit here was half a century ago. In the aftermath of that tsunami, they built these ten metre high sea walls, far higher than anyone thought they would need. (Siren) Tsunami drills became a regular feature of life. Everyone knew what to do when the siren sounded. On March 11, all along the coast the sirens did sound, this time for real. Go to the hill! A tsunami was coming, this was not a drill. WOMAN: Can you hear the sirens? (Sirens) MAN: There's a hill outside of town that we're going to try to get to. (Sirens) It's a precautionary measure, but you never know, this town has a lot of history with tsunamis and a lot of death from it, so they're taking it pretty seriously, obviously. (Sirens) The warning saved the lives of some. This footage captures the moments after the sirens sounded. MAN: Here it comes! The tsunami breached the coastal defences. Miyako's high walls proved useless. Countless people died here. The tsunami was ten metres high. Why did their ten metre high walls fail to stop it? With thousands of sensors along the coastline, the scientists already have part of the answer. The fact that the shoreline has actually subsided means that the sea had plenty of space to go and it basically filled up the empty space left by the sinking. Several villages have just been completely ruined with no survivors. And the human death toll is obviously going to be up in the tens of thousands when the final count is in. The data from the sensors had revealed something incredible. The earthquake had caused the whole coastline to drop by up to a metre, lowering Miyako's walls, making the tsunami much worse. All along the coast, subsidence put towns in danger. You've got the tsunami wave coming in, you know, on top of what would be essentially a two metre higher vacuum of subsided land as it sweeps in and there's not much to stop it until it hits higher ground somewhere. But most at risk was the shut down nuclear power plant at Fukushima. It had survived the earthquake, and here too there was a 5.6 metre defence wall, but now it had sunk over half a metre. 40 minutes after the quake, the waves smashed over the wall and flooded the diesel generators that were cooling the reactor cores. Back up batteries kicked in, batteries with just an eight hour charge. With thousands already confirmed dead, and now the threat of a nuclear diaster, Japan was in crisis. Overnight, fires raged across a sea flooded wasteland. Oil from factories and gas from ruptured lines set hundreds of square kilometres of debris ablaze. In Tokyo, the train system was paralysed. Millions bedded down in offices and waited for dawn. Meanwhile, the tsunami wave was still spreading across the ocean at 800 kilometres an hour. Countries all around the Pacific rim were watching the situation nervously. In Hawaii, the Tsunami Warning Center was on full alert. Very quickly we realised that this was, this was basically the first big ocean crossing tsunami that had happened in 40 years. Frantically they were trying to work out when and where the wave would strike next. At that point we went to a Pacific wide warning which means another message and now lots and lots of phone calls. State warning point. This is the Pacific Tsunami Warning Center. Hawaii issued an evacuation alert. People headed to higher ground. The wave that hit was one metre high. It caused damage but thankfully the distance had weakened the wave. This time no lives were lost. With the wave now fading, countries around the Pacific downgraded their alerts. But Japan awoke to a nightmare. Different parts of the shoreline had suffered different effects. Channel 4 journalist Callum Macrae set off along the Japanese coast to compare the levels of destruction and discover how far-reaching the damage of the tsunami was. (Bell) He was the first journalist to reach the isolated mountain community of Kohoku. We are up in the mountains, eight kilometres from the coast, and what's happened here is that the tsunami has created a huge surge which has climbed all the way up the river and then flooded here. Amazingly, this lake of seawater is metres above sea level. The locals here fear that as the waters recede it will expose bodies swept all the way up from the coast. Travelling north, at first the town of Ofunato seems untouched. Look over there, those houses look undamaged, and they've got power and everything here. It's just so strange. Closer to the shore it was a different story. And as if Ofunato didn't have enough problems, scientists reckon that this whole area, this region, has subsided well over a metre and in the next couple of days they're also expecting their highest tides of the year. The sea is some 500 metres down there and yet up here we have this. It's a remarkable sight by any standards, a huge tug which has been brought all the way up here by the tsunami. And what's remarkable about it, well, what's even more remarkable about it, is that what is says about the size of the tsunami because the Japan meteorological centre just produced provisional estimates saying that the tsunami that hit this region was about 3.5 metres high. Now, we're seven, eight metres above sea level here, and even given the surge, the fact that it could bring that all the way up here does suggest that the tsunami here was a lot higher than 3.5 metres. Even amidst such chaos this seems strange. Boats, trucks and cars were dumped on top of buildings, much higher than the recorded height of the wave That happens because as the water is pushing through restricted areas like the streets of towns and villages, it's being effectively funnelled and the water's got to go somewhere and so it goes up as it's squeezed and funnelled and pushes materials, pushes cars, onto roofs, sometimes as high as 50 feet. So in areas, the impact of this would be even greater, particularly where you get narrow streets. Once the wave starts to pick up part of a town, the warehouses along the dock, the debris and all that, then it becomes more like a glacier, you know, it's a moving wall of debris and the more mass it has, the more power it has as it comes in. It doesn't really look like water beyond some point, it looks like the entire town is flowing in, and it is. So all the mass of all the buildings, cars, refrigerators, everything that's in that wall, it's essentially a debris glacier at that point and it just keeps coming in. This is Minamisanriku, the town that was wiped of the map. 95% of the buildings destroyed. Over 10,000 people, half the population, missing. This place, Minamisanriku, probably symbolises the tragedy more than anywhere. An entire town wiped out by the force of nature. It's almost difficult to imagine one's thoughts as one sees this coming towards you. And as it hits the coast it's then picking up all the debris it's picking up buildings, cars and things, and you then end up with this, sort of, really quite horrific mass moving through towns, villages, across fields, causing complete destruction. I mean, it would be bad enough if it was only water, but because it's full of cars and you can't, you can't swim against it or flow with it or do anything, you're just in a, like in front of a bulldozer moving the entire town. (Siren) It's funny that when you hear that sound of an ambulance it kind of, actually gives you hope that they might've found somebody alive. Although, that must be happening fewer and fewer times between. Anyone who did survive and was trapped would almost certainly have died of hypothermia by now. At the town of Rikuzentakata, rescue workers hunt for survivors, and discover the dead. When they find a body, they put a large stick in the ground with a flag attached to it so that it can be recovered later. It's a fairly gruesome and sad task. In fact, they're not just collecting bodies, they're also collecting personal mementoes as well which they find. Like this. I'm afraid what we have here is more bodies waiting to be taken away. As Professor Roger Bilham returns to Tokyo from his aerial survey the city's vulnerability becomes all too clear. There are 30 million people within about two metres of sea level and a tsunami here of course would be absolutely devastating. Suddenly, a problem. PILOT: We had a big earthquake just now, so... Really? Yeah. We've just learned from the ground that there was an earthquake that damaged the heliport. They're checking for damage right now. We don't know how big the earthquake was, but it was obviously a nearby aftershock. A massive aftershock has hit Tokyo, magnitude 6.2. In the week that followed the main quake there were over 500 aftershocks along the fault. This is the actual data from seismometers around Japan. The larger the circle, the bigger the aftershock. The shaking has now stopped so I'll just continue landing. Finally, Bilham's helicopter is given the all clear to land. Even at the heliport in Tokyo, the damage is plain to see. I notice that the tarmac here which should be beautifully dark everywhere is in fact stained white in places and you can see that black sand has come out of this crack and there's another one over there, another one over there. We're very close to the shoreline and the lurching motion of the ground during the earthquake has caused the subsurface liquefied sands to come belching out on the top. Precisely the same phenomenon, liquefaction, that was filmed during the earthquake. And over here is an old mud volcano. Old, it's about three days old. You can see how the mud came pouring out of the top there. So, look, we're 200 miles from the epicentre here and here's a crack in the heliport landing area. It continues all the way along here. You can actually see down about three feet in places. Splits into two here. This goes over here. You can see an offset in the, um, in this trim around the tarmac. As the earth's crust shattered during the main quake, new stresses spread along the fault. Relieve the pressure in one place and it builds up elsewhere triggering aftershocks. What you're seeing here is how those aftershocks happened over a period of about a week after the main shock. And that orange region delineated by those orange dots essentially gives you a feeling for the area of the fault along the plate boundary that ruptured in this event. Every aftershock takes its toll on an already frightened population. Journalist Callum Macrae has been moved by the plight of the people here. In the regional capital of Sendai, the temporary shelters are full. But in the darkened, ravaged city it seems one person at least is trying to cling to normality. We're in Sendai, 300 or 400 metres from the shorefront in a scene of apocalyptic chaos. It's cold, it's dark, there's no power anywhere and yet up there in that abandoned block of flats, on the top floor, there's one light. One man, one family perhaps trying to survive in this chaos. The following day on the road back to Tokyo. The arterial road that connects the north and south is empty. A reminder of the damage this disaster has done, and is still doing. REPORTER: This is already one of the worst nuclear accidents in history if it stops right now. And we're dealing with multiple meltdown possibilities. WOMAN: Two radioactive substances, caesium and iodine, were detected near the number one reactor at the plant on Saturday. The Fukushima nuclear base is about 60 kilometres that way, that's about 38 miles or so, I think. And, you know, we've got the windows closed, we're driving fast, who knows whether it's safe? The advice is very conflicting. The American government says that, ah, has put an exclusion zone of 80 kilometres and, of course, we're well within that. On the other hand, the Japanese government say it's fine as long as you're more than 30 kilometres away. So, I mean, who can tell? Nobody knows. But, ah, we'll keep the windows closed and I'll put on a mask. Mask. Looks good, huh? The danger posed by the Fukushima nuclear plant remains unresolved. Meanwhile, scientists have started to analyse the startling number of aftershocks that are still rattling Japan That main shock was followed by hundreds of magnitude fives and dozens of magnitude six earthquakes and a handful of magnitude sevens. One you had a pattern of an earthquake happening, followed by a bigger one, you never know if it's going to happen again. Japan's earthquake warning systems did and will save lives. The Hawaii tsunami warning system also saved thousands. As the tsunami crossed the ocean, the warning centre monitored it all the way. Here it is here. We couldn't let our guard down because, of course, the tsunami has continued on and we have a continuing responsibility to the rest of the Pacific. Even though the tsunami lost most of its energy as it crossed the ocean the scientists had been able to warn the world. As the tsunami spread across the ocean, at location after location we realised, 'Oh, our predictions are pretty darn good.' Because people were warned, there was very little destruction or damage, certainly to human life. One person did lose their life, in California, north of Crescent Bay, because they rushed down to the beach to take photos of the tsunami as it came in. In Japan, the humanitarian disaster continues. Estimates put the death toll from the quake and tsunami at over 20,000. Rebuilding will take generations. For scientists, the analysis continues. From all the data they have acquired, one threat is still very clear. Experts have warned of a large quake and tsunami off the coast near Tokyo for years. The fault lines under the ocean to the south of Tokyo are dangerously stressed, but this time the earthquake happened in the north. What's been expected is a slip of the Philippine plate relative to the Eurasian plate. What's actually occurred, is a slip of the Pacific plate relative to the Eurasian plate. Sometimes a great earthquake will cause the next patch of the plate boundary to slip. So all eyes are on what's happening, how this earthquake has stressed the neighbouring part of the plate boundary. This whole region is in a very high state of stress, it's ready to go, and they've been expected to go at any minute. So this recent earthquake is going to have brought that closer. The question is, how much closer? When an earthquake like this happens it...basically, all of the stress that it relieves in the earth's crust essentially gets transferred somewhere else. It doesn't go away. It actually adds loading to other parts of the crust. The densest areas of population survived largely unscathed. Next time could be different. One area of extreme concern is Tokyo, the world's largest city. There could be a major event in Tokyo that would be extremely damaging to this very densely populated region. If you were going to chose to put one of the major industrial economies on the planet, that part of the Pacific rim is not the place you would choose. It could be happening as we speak, or it might not happen for a decade. The critical thing is, has this particular earthquake shaken that region up so that it brings forward the timing of that earthquake? It's foolish to think we can stop natural phenomenon. What we've got to do is to learn to live with them and minimise the consequences when they happen and minimise also the recovery time. It's very difficult for science to protect against earthquakes and tsunamis. What science can do is help town planners, engineers, to make buildings stronger, to make designs of buildings and cities more resilient. We cannot stop these things happening. We can't prevent it, but we can prepare for it. Closed Captions by CSI