Meltdown: Earthquake, Tsunami, and Nuclear Disaster in Fukushima

by Deirdre Langeland

  In the end, most of the severe damage caused by the quake was the result of liquefaction. Cities built near major bodies of water often create new land by dumping soil and rubble, called landfill, into bays and ocean inlets. Under normal conditions, this reclaimed land is a perfectly stable base for buildings and parks. But when an earthquake shakes landfill, it can spell trouble, especially when the surrounding soil is sandy.

  Sandy soil can store a lot of water. The grains of sand are stacked haphazardly, with water molecules between them. But when the soil is shaken, the structure holding up the grains collapses, causing water from below to rise toward the surface. Each shake makes more grains sink and more water rise, building up water pressure in the soil. When the pressure is great enough, the ground begins to move like a liquid. When that ground is underneath a building or a road, the result can be catastrophic.

  The four main types of seismic waves each have distinct characteristics. Primary waves and secondary waves are body waves—they travel through the layers of the Earth beneath the crust. Primary waves are the only kind that can travel through both solid rock and molten lava. They radiate through Earth’s mantle and core, having little effect on Earth’s surface. Secondary waves move through the solid rock of the mantle, but cannot penetrate the molten iron outer core. They cause some damage to the land above. Love and Rayleigh waves are surface waves, and produce most of the shaking felt during an earthquake.

  A woman named Yukari Kurosawa was working at a hospital in Otsuchi when the quake struck. Afterward, she described the effects of liquefaction—indoors and out. “Suddenly everything started to shake,” she remembered. “Even the heavy desk, which always took so much effort for us to move, was jigging up and down like a toy.” When a coworker shouted at her to get out of the building, she moved to the parking lot, where the ground beneath the pavement had liquefied. “Outside, the asphalt was rolling and heaving. ‘Asphalt waves,’ I thought when I saw it.”

  All around Japan, sections of parking lot and road seemed to turn to liquid. The metal tubes lining manholes popped out of the pavement as the ground around them sank and settled. In Chiba City, where parkland had been created on landfill dumped into Tokyo Bay, the sidewalks rippled like fabric. The ground sloshed and swayed, and water spurted rhythmically from the lawn, sounding like waves lapping on a shore.

  Light structures like this bus stop were shaken apart by the quake.

  Just outside of Chiba, at a refinery owned by Cosmo Oil, a huge storage tank had been filled with water—instead of the lighter natural gas it was meant to hold—for inspection. Braces reinforcing the legs of the overburdened tank snapped during the heavy shaking of the earthquake. About a half hour later, the tank’s legs buckled and broke, sending it crashing into a pipeline carrying fuel. As a mixure of propane and butane poured from the broken pipe, flames spread across it, crawling along the ground until they reached a nearby fuel tank. It exploded, spreading the fire to another tank, and another, and another. It would be ten days before firefighters were able to put the fire out completely.

  The tank collapse at the Cosmo Oil refinery caused a fire that raged for more than a week after the earthquake.

  In Fukushima prefecture, the shaking rattled Sukagawa, a town about 40 miles from the coast. It sent the Fujinuma Dam sliding nearly 15 feet downhill, and water from the reservoir behind it began to spill over its top. About twenty minutes after the earthquake, the water pouring over the dam caused it to collapse entirely, flooding nearby homes and killing eight people.

  But despite these tragedies, the most remarkable thing about the Great Tohoku Earthquake was how well the Japanese system worked. When the shaking subsided, about 26,600 houses had been destroyed, and 1,476 people were dead. In comparison, the Kobe Earthquake of 1995, with a magnitude of 6.8, had killed 6,308 people. The Tohoku quake, at magnitude 9.1, was more than 100 times more powerful.

  Such a massive quake could have caused damage much, much worse. By magnitude-9 standards, the country had fared well.

  That was before the tsunami.

  tsunami

  Friday, March 11, 2011

  Reactor Status

  Reactor 1: Scrammed

  Reactor 2: Scrammed

  Reactor 3: Scrammed

  Reactor 4: Shut down for inspection

  Reactor 5: Shut down for inspection

  Reactor 6: Shut down for inspection

  After the earthquake, people all over Japan were in shock. They began to take stock of the damage, checking in with classmates, family members, and neighbors. The violent shaking had shattered glass, fragmented roads, toppled telephone poles, collapsed bus shelters and sheds. Indoors, rooms that had been neat and orderly five minutes earlier looked like they had been ransacked. Bookshelves and dressers had capsized, scattering their contents everywhere.

  But it wasn’t just furniture and buildings that had shifted—when the Japan Trench ruptured, the shape of the entire planet changed. A NASA scientist later calculated that the movement of rock, magma, and soil had shifted Earth’s center of gravity, causing the planet to spin a microsecond faster. (A microsecond is one millionth of a second.) The Pacific Plate had slid westward, but the North American Plate had also jumped. When the quake was over, parts of the island of Honshu were as much as 13 feet farther east than when it began.

  Honshu didn’t move. It stretched. For thousands of years, the North American Plate, caught between the Pacific and Eurasian Plates, had been squeezed by the two larger plates. It had compressed, gradually squashing into a smaller space. But it had also bowed, curving and collapsing a little like a kitchen sponge when you squeeze it between your thumb and fingers. As the Pacific Plate slipped westward, the North American Plate sprang back toward its original shape. This left parts of the island’s east coast farther from its western edge. The elevation of this area changed, too. As the arch flattened, as much as 250 miles of coastline—roughly equal to the distance from New York City to Washington, D.C.—sank by 2 feet.

  At the fault, about 60 miles east of the Honshu coast, 190 miles of seafloor along the edge of the North American Plate leaped upward by about 30 feet. That displaced—pushed away—millions of gallons of water. The water had to go somewhere.

  Have you ever dropped a rock into a puddle or a pond? Water splashes up when the rock breaks the surface, and circular ripples spread out from the point where it entered the water. This is an example of displacement on a very small scale. When the rock falls in, it takes up space that used to be occupied by water, so the liquid has to move out of the way. Some of it leaps from the surface as a splash, and some of it forms a circular ripple, a series of tiny waves radiating from the rock’s entry point.

  The release of the North American Plate during the quake caused its outer edge to leap upward, displacing the water above it. At the same time, land near the shore flattened, causing a drop of about two feet along the coast.

  In an earthquake, the effect is similar, but the displacement comes from below. When the seafloor springs up, it shoves millions of gallons of water upward and outward. On the surface, the water creates waves much like the ripple made by the rock. But on this much larger scale, those ripples form a tsunami.

  In the open ocean, a tsunami moves incredibly fast—up to 500 miles per hour. The waves are pretty small, usually only a few feet high, and they could be separated in time by as much as an hour. Ships at sea don’t notice tsunami waves. As they pass beneath the hull, they feel like any other ocean swells. But unlike most waves, which disturb only the water near the surface, the movement of a tsunami extends all the way to the ocean floor. The entire ocean surges forward at breakneck speed. As the tsunami reaches shallower water near land, it begins to slow down. The shallower the water is, the slower the waves are—but they grow taller.

  Imagine an entire classroom of kids walking in line to the playground. Better yet, imagine them running. If the first kid in line stops, or even just slows down dramatically, the kids behind will crash
into her. The ones at the back will quickly catch up and run into the ones who have piled up in front. The same thing happens with water. As the front of the wave slows, the water behind it piles on. All that water surging forward needs to go somewhere, so it goes upward. The wave grows taller. Exactly how tall the wave becomes, and how fast it is going when it hits land, depends on the shape of the ocean floor and of the shoreline it is approaching.

  If the prospect of a giant wave doesn’t sound so bad to you, consider this: 1 cubic yard of water (enough to equal about the size of a washing machine) weighs about 1,700 pounds. Rushing water 6 inches deep is strong enough to sweep adults off their feet. A foot of rushing water can carry away a car. And, although a tsunami near the shore is moving slower than it was at sea, it’s still moving faster than a car on a highway, usually about 100 miles per hour. In other words, a tsunami strikes land like a line of Mack trucks moving at top speed.

  Like all tsunamis, the waves generated by the Great Tohoku Earthquake traveled across the ocean without slowing down. The tsunami would reach Crescent City, California, more than 5,000 miles away, as an 8-foot-high wave almost ten hours later. In eighteen hours, it would hit the Sulzberger Ice Shelf in Antarctica, where it would knock loose an iceberg twice the size of Manhattan. But long before it reached those shores, it would strike Japan.

  * * *

  Japan has a long history of tsunamis. The word itself—tsunami—is Japanese. While tsunamis can occur anywhere in the world, the shape of the coast in the Tohoku region makes them particularly devastating. The northeastern shore of Honshu, often called the Sanriku Coast, zigzags in and out, forming jagged shapes that resemble the teeth of a saw. Rias, riverbeds that have been flooded by the sea, form deep harbors that reach inland, creating channels that can funnel waves. The riverbeds provide a perfect path for a tsunami to flow inland and high up mountainsides.

  On the Sanriku Coast, which extends through Iwate and Miyagi prefectures, the shoreline zigzags in and out like the teeth of a saw.

  In the area around Otsuchi, the land alongside those rias flattens out for miles, making it ideal for farming. But when a tsunami comes, that farmland becomes a wide floodplain that is difficult to escape in a hurry.

  From an early age, children in Tohoku are taught an evacuation strategy called tendenko. Precious time is lost when parents go searching for their children or neighbors stop and check in on each other—or, worse yet, if people are left waiting for help. It may seem ruthless, but the strategy is simple: When a strong earthquake strikes, a tsunami is likely following close behind. Each person should evacuate separately to a safe place. Do not stop. Do not look for others. If everyone follows tendenko, then people can be confident that their children, parents, neighbors, and friends are getting out of harm’s way—there will be no need to check on loved ones. Each person is free to evacuate quickly.

  That sound advice has rippled through coastal towns for centuries. Misa Koshida, a grandmother in Otsuchi, remembered hearing these words of wisdom when she was a child: “Never call out to others when you flee from a tsunami, because you will find yourselves standing around talking to each other. Just run away, and never, ever turn back.”

  Another Otsuchi resident, Yukari Kurosawa, was told a simpler adage when she was young: “If a big earthquake hits and the ocean draws back, run!”

  Children practice tendenko during a tsunami drill held on Okinawa on the fifth anniversary of the tsunami.

  Unfortunately, tendenko is easier to follow in theory than in reality. The Great Tohoku Earthquake struck during the workday, and after the shaking stopped, the first impulse of many residents, panicking because of the unusual strength of the earthquake, was to head for home. In Japan, many families live in multigenerational households, and people were concerned about elderly parents and grandparents. They rushed in the wrong direction.

  Some were also confused by a glitch in the earthquake early warning system. Earthquake and tsunami warning systems have to act quickly, with limited data. In the first minutes after the fault ruptured, the Japan Meteorological Agency (JMA) estimated the magnitude of the quake at 7.9. Three minutes after the quake began, the agency issued a tsunami warning predicting waves up to 20 feet high in Miyagi prefecture and 10 feet in Iwate and Fukushima.

  To residents of coastal towns in those regions, the height of the wave made all the difference. Seawalls protected most of the villages and towns on the Japanese coast. The walls varied in height depending on the town, but most were about 20 feet tall. They could easily deflect a 15-foot wave. A 25-foot wave might overflow the barriers, causing minor flooding and damage. But a 40-foot wave would easily overtop the walls and destroy everything in its path.

  Minutes after the first warning, the tsunami swept past a GPS buoy, which measured its height. Based on those measurements, JMA issued a new warning about twenty-eight minutes after the earthquake. It predicted waves higher than 30 feet in Miyagi, and 20 feet in Iwate and Fukushima. For most, however, the revised warning arrived too late. The first waves reached the shore between fifteen and thirty minutes after the earthquake. They had already swept inland by the time the revised warning arrived.

  JAMA uses GPS buoys to detect changes in ocean height offshore and send an alarm before a tsunami reaches the shore. The buoys include GPS systems, transmitters, and solar panels. Satellites register changes in the buoys’ position and transmit the data back to a base station, which issues alerts.

  In the town of Ishinomaki, dead center along the coast of Miyagi, residents were lulled into a false sense of security by the early tsunami predictions. After the earthquake, children and teachers at the Okawa Elementary School streamed out the doors wearing plastic safety helmets, standard equipment at any Japanese school. Nearby residents, who used the school as an evacuation center, joined them. Two and a half miles from the shore, they assumed they were safe. A few kids were picked up by worried parents. The rest—eighty students and twelve teachers—waited out the danger on the flat school grounds. Behind them was a 725-foot hill they could easily have climbed to safety.

  Despite the confusion caused by the early tsunami predictions, hundreds of thousands of residents along the Tohoku coastline did flee. Buildings very close to the shore were clearly in danger. Evacuation sirens blared, and loudspeakers warned anyone within earshot to leave the area. And many wisely followed tendenko. But evacuation proved difficult. In the moments after the earthquake, smaller, secondary earthquakes, called aftershocks, continued to rattle the landscape. At the Otsuchi hospital, Yukari Kurosawa decided to walk home to check on her elderly mother. She didn’t get far. “As I was crossing the bridge close to the hospital,” she later remembered, “an aftershock hit and the bridge swayed wildly. If the bridge collapsed, I knew I’d die … so I turned back.”

  Those who tried to flee by car didn’t fare much better. Roads were clogged with traffic. In some cases, they had crumbled.

  Even as ordinary citizens fled to safety, emergency workers raced for the floodgates. Rivers and inlets from the sea provide an easy route for incoming waves, carrying tsunamis much farther inland than they could otherwise travel. Seawalls can’t run across these inlets—the water needs to be able to flow back and forth under regular conditions. The solution is to build a dyke with floodgates—sliding panels that can be closed to seal off the opening—across the mouth of the river. The job of closing those massive gates fell to fire brigades.

  Nestled between two mountains, the village of Fudai was a sitting duck for an incoming wave. The hills on either side of a cove would direct the water right down the middle, funneling it toward the village. But a 51-foot floodgate and an equally high seawall spanned the gap between the hills. After the earthquake struck, firefighters activated electric panels in the floodgate remotely, and most slid shut. But smaller side panels, probably damaged by the earthquake, wouldn’t close. Four firefighters rushed to the jammed floodgate and struggled to fire up a backup generator. As they worked, the seawall blocked
their view of the ocean, so they couldn’t see what was coming. But they could hear it.

  Before a tsunami arrives, the sea grows still. The water draws away from the shore, toward the approaching wave. People who have spent their entire lives surrounded by the constant rhythmic noise of the sea are suddenly met with silence.

  And then the tsunami barrels in.

  Survivors describe the sound of a tsunami as everything from a deafening rumble to a rasping hiss. The wave itself roars like a jet engine. As it moves, it picks up everything in its path. Giant ships, entire buildings, trucks, trees, and power poles snap, crunch, and grind.

  The seawall at Fudai is 51 feet tall. Floodgates (blue) can be opened and closed to control the flow of water beneath the wall.

  In Fudai, the firefighters heard the growing thunder of an approaching wave as the stubborn panels slowly ground closed. They sped for safety as the monster wave poured over the seawall behind them.

  * * *

  For fifty-three-year-old Toshikazu Abe, the tsunami announced itself with an explosion. He had rushed home after the earthquake to check on his mother. Outside, loudspeakers were blaring an evacuation warning. Abe heard the warnings, but he didn’t really believe the water could reach his home. Then he heard an explosion outside. “I heard a loud sound—bam!—like a telephone pole falling to the ground. I went out onto the balcony and saw a mountain of rubble surging right in front of me—parts of buildings, boats, household objects. I stood there in stunned silence. The next moment, I was swept away by a giant wall of water and debris.”

  A wave of the tsunami pours over a seawall meant to protect the city of Miyako, about 150 miles north of Sendai, on March 11, 2011.