On March 11, 2011, an earthquake struck off the coast of Japan, producing a devastating tsunami that sent walls of water washing over coastal towns, cities and farmland in the northern part of the country and set off warnings as far away the west coast of the United States and South America. Recorded as 9.0 on the Richter scale, it was the most powerful quake ever to hit Japan and the seventh strongest ever recorded globally (tied for forth since 1900). It was also Japan's worst natural disaster since World War II (earlier earthquakes and tsunamis killed more people).

In Japan it became known as the Great East Japan Earthquake and Tsunami or the Tohoku Pacific Offshore Earthquake (Japanese refer to northern Honshu, especially the northeast side of the island as Tohoku). The coastal areas of Iwate, Miyagi and Fukushima prefectures suffered particularly severe damage, due to devastating tsunami more than 10 meters high. Joshua Hammer wrote in the New York Times, “The devastation stretched along hundreds of miles of seacoast; towns washed away by mudslides; trains carried out to sea; thousands of survivors left stranded on roofs, awaiting rescue. The quake also led to... the partial meltdown of at least two nuclear reactors. Only the fact that the epicenter was not near a densely populated area prevented far greater casualties.”

The 9.0- magnitude earthquake was so powerful it shifted the position of the Earth’s figure axis by as much as 15 centimeters and moved Honshu, Japan’s main island, two and half meters eastward. The tsunami generated by the earthquake obliterated towns and damaged hundreds of thousands of buildings, including four reactors at the Fukushima Daiichi nuclear power plant. The cost of disasters worldwide was the highest ever in 2011 ($380 billion), mainly due the earthquake and tsunami in Japan.

A total of 196,559 buildings were destroyed or damaged. Around 27,000 people were killed. More than 460,000 were made homeless and sought refuge in shelters. This included 150,000 in Miyagi Prefecture, 47,000 in Iwate Prefecture and 130,000 in Fukushima Prefecture. In the first three days after the disaster Japan’s Self Defense Forces (the Japanese military) rescued 66,000 people, many of them stranded on hilltops and rooftops and among debris. Because reaching them by land was so difficult many had to wait to be retrieved by helicopter, which could carry only a few people at a time. Thousands of others evacuated their homes due to the crisis at the Fukushima nuclear power plant.

The Maximum of 7 on the Japanese seismic scale was recorded in Kurihara, Miyagi Prefecture. Upper 6 was recorded in 34 cities and towns in Miyagi, Fukushima, Ibaraki and Tochigi prefectures. The scale of the disaster took some time to absorb. Headlines in the newspaper the day after the quake read: “At least 20 dead...and some houses were washed away.” By the time these papers were reaching the streets television video was showing massive black waves swallowing up houses and cars and vast empty spaces where towns used to be. Bodies washed ashore at various spots along the coast after having been pulled out to sea by the tsunami’s retreat and then pushed back to the shore. Japanese Prime Minister Naoto Kan told a press conference: “I think that the earthquake, tsunami and the situation at our nuclear reactors makes up the worst crisis in the 65 years since the war. If the nation works together, we will overcome.”

According to the U.S. Geological Survey, there have been only five quakes of magnitude-9.0 or greater since 1900. The strongest was a magnitude-9.5 quake that hit Chile in 1960, and all five were ocean trench earthquakes. The Great East Japan Earthquake is the fourth-strongest on record. The energy of a magnitude-9.0 quake is 32 times greater than that of a magnitude-8.0 quake. [Source: Yomiuri Shimbun, April 30, 2011]

Websites, Links and Resources



Good Websites and Sources on Tsunamis: Wikipedia article on Tsunamis Wikipedia ; Surviving a Tsunami, Lessons from Chile, Hawaii and Japan ; Tsunami Warning System in Japan ; Tsunami Warnings from Japan Meteorological Agency ; Book: Tsunami: The Underrated Hazard by Edward Bryant. Tsunamis That Struck Japan Major Tsunamis in Japan in the 20th Century ; Major Earthquakes and Tsunamis in Japan in the 20th Century ; 1933 Earthquake and Tsunami pdf file ; 1983 Tsunami ; Report on the 1993 Tsunami ; Small Tsunami in 2010 ;

Good Websites and Sources on Earthquakes: U.S. Geological Survey (USGS) National Earthquake Information Center ; Wikipedia article on Earthquakes Wikipedia ; Earthquake severity ; USGS Earthquake Frequently Asked Questions ; Collection of Images from Historic Earthquakes Pacific Earthquake Engineering Research Center, Jan Kozak Collection ; World Earthquake Map ; Most Recent Earthquakes ; Interactive Earthquake Guide ; USGS Earthquakes for Kids ; Earthquake Preparedness and Safety Surviving an Earthquake ; Earthquake Pamphlet ; Earthquake Preparedness Guide ; Earthquake Safety Site ;

Earthquake Information for Japan Earthquake Information from Japan Meteorological Agency ; F-Net Broadband Seismography Network ; USGS Japan Earthquake Information ; Tectonics and Volcanos of Japan ; MCEER Earthquake Engineering on Major Earthquakes in Japan in the 20th Century ; Major Earthquakes in Japan in the 20th Century ; Sesimic Hazard Map ; Earthquake Density Map ; Seismicity Map ; Blogs About Japanese Earthquakes ; Geological Maps ; Earthquake Engineering and Disaster Prevention: Disaster Prevention Research Institute, University of Kyoto ; Japan Association of Earthquake Engineering ; Earthquake Preparedness in Japan Earthquake Preparedness Survey ;U.S. Embassy Disaster Preparedness Checklist ; U.K. Embassy on Earthquake Preparedness v ; Report on Fastening Furniture pdf file ;Earthquake Preparedness Guide ;

Earthquake Research in Japan: Headquarters of Earthquake Research Promotion ; Active Fault Research Center ; Institute of Geology and Geoinformation ; Tokai Earthquake Prediction from Japan Meteorological Agency ;Research Center for Earthquake Prediction, University of Kyoto ; Earthquake Prediction Research Center, Tokyo University ; Earthquake and Science Museums Shinagawa City Disaster Prevention site ; Earthquake Museum (Kita Ward, near the Nishigahara Station on the Naboku subway line), Tokyo Essentials ; Honjo Life Safety Learning Center (Sumida Ward) simulates an earthquake and fire in a 3-D theater. There is also a room that simulates a storm with wind sped of 30 meters per second. Tokyo City PDF file

Recent Earthquakes in Japan : USGS Last Earthquake in Japan ; Recent Earthquakes ; Info for the Previous Week ; Major Earthquakes in Japan Wikipedia List of Earthquakes in Japan Wikipedia ; USGS Historic Earthquakes ;Major Earthquakes in Japan in the 20th Century ; 1923 Tokyo Earthquake: 1923 Tokyo Earthquake Images ; Great Kanto earthquake of 1923 ; 1923 Tokyo Earthquake Photo Gallery ; Earthquake Pictures: Earthquake Image Archive ; BBC Pictures of 2007 Niigata Earthquake BBC Pictures of 2007 Niigata Earthquake ; Kobe Earthquake Site

Death Toll From the Earthquake and Tsunami of 2011

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Kesennuma Before
Death toll as of March 2012: 15,854 in 12 prefectures, including Tokyo and Hokkaido. At that time a total of 3,155 were missing in Aomori, Iwate, Miyagi, Fukushima, Ibaraki and Chiba prefectures. The identities of 15,308 bodies found since the disaster, or 97 percent, had been confirmed at that time. [Source: Japan’s National Police Agency]

As of September 2011, the National Police death toll was 15,774 dead and 4,227 missing. Even at that time the search for bodies was still continuing in the no-go zone around Fukushima nuclear power plant. As of June 11 the death toll reached 15,413, with about 2,000, or 13 percent , of the bodies unidentified. Around 7,700 people were missing. As of May 1, 2011: 14,662 were confirmed dead, 11,019 were missing, and 5,278 were injured. As of April 11, 2011 the official death toll stood at than 13,013 with 4,684 injured and 14,608 people listed as missing. The true death figure is hard to determine because there may be some overlap between the missing and dead and not all residents or people in areas devastated by the tsunami can be accounted for. The final toll is expected to exceed 27,000.

The disaster hit Ishinomaki---a farming and fishing community of 160,000 about 50 kilometers northeast of Sendai---hard. Of 8,000 people still missing across northeastern Japan, 2,770 are from Ishinomaki; it also has the highest confirmed death toll, 3,100. Of 17,000 residents in Minamisanriku, 1,000 were killed.

A large number of victims were elderly and from Miyagi Prefecture . When the death toll topped 10,000 on March 25: 6,097 of the dead were in Miyagi Prefecture, where Sendai is located; 3,056 were in Iwate Prefecture and 855 were in Fukushima Prefecture and 20 and 17 were in Ibaraki and Chiba Prefectures respectively. At that point 2,853 victims had been identified. Of these 23.2 percent were 80 or older; 22.9 percent were in their 70s; 19 percent were in their 60s; 11.6 percent were in their 50s; 6.9 percent were in their 40s; 6 percent were in their 30s; 3.2 percent were in the 20s; 3.2 percent were in their 10s; and 4.1 percent were in 0 to 9.

The conclusion that one draws from this data is that relatively young people were better able to make a dash to safety while the elderly, because they were slower, had difficulty reaching high ground in time.

A forensic examination of 126 victims recovered in the first week after the disaster in Rikuzentakata by Hirotaro Iwase, a professor of forensic medicine at Chiba University, concluded that 90 percent of the town’s fatalities were caused by drowning. Ninety percent of the bodies had bone fractures but those are believed to have occurred primarily after death. The autopsies showed that the victims had been subject to impacts---presumably with cars, lumber and houses---equivalent to a collision with a motor vehicle traveling at 30 to kph. Most of the 126 victims were elderly. Fifty or so had seven or eight layers of clothing on. Many had backpacks with items like family albums, hanko personal seals, health insurance cards, chocolate and other emergency food and the like. [Source: Yomiuri Shimbun]

Before the March 11, 2011 quake the most devastating earthquake was the Great Tokyo Earthquake of September 1, 1923, event, which registered 7.9 on the Richter scale, lasted about five minutes, and flattened Tokyo and the port city of Yokohama, killing 140,000 people. There have been several earthquakes and tsunamis in Japan’s history that have killed between 10,000 and 30,000 people.

First the Earthquake

Kesennuma After
On Friday, at 2:46 p.m. Tokyo time, the quake struck. First came the roar and rumble of the temblor, shaking skyscrapers, toppling furniture and buckling highways. Japanese, accustomed to frequent earthquakes, were stunned by this one’s magnitude and the more than 100 aftershocks, many equivalent to major quakes.”I never experienced such a strong earthquake in my life,” Toshiaki Takahashi, 49, an official at Sendai City Hall told the New York Times. “I thought it would stop, but it just kept shaking and shaking, and getting stronger.” In Tokyo it was strong enough to bend the top of Tokyo Tower.

Chico Harlan wrote in the Washington Post, “For those in Tokyo, the earthquake rattled buildings, shook offices. Computers spilled, lights gyrated and workers ducked under desks. But in Sendai, the capital of Miyagi Prefecture, the tsunami turned a city into a confetti of shrapnel and wood---car scraps, engine parts, bricks. Eventually the wall of water that crashed ashore left behind a dark sludge that coated surrounding farm areas. At the Sendai airport, fire soon burned from a small building positioned between the terminals. Cars and propeller airplanes were discarded by the waves, left among splintered wood, and aerial photos made them appear much like toys left out on the floor.” [Source: Chico Harlan, Washington Post, March 12, 2011]

Eight days before the quake a 7.2-magnitude earthquake occurred off the north coast of Honshu not far from epicenter of the main March 11 quake. Tsunami warnings were issued but the tsunamis that came ashore were only about 50 or 60 centimeters in height. There were no reports of injuries or serious damage. The next day a 6.8-magnitude quake rocked the region.

Japanese Government at the Time of the Earthquake

Eric Talmadge and Mari Yamaguchi of AP wrote: “On March 11, Prime Minister Naoto Kan was taking a beating in an Upper House committee meeting over whether he had taken campaign money from a foreign national, which is illegal in Japan. The questioning stopped suddenly when the entire parliament building, a sprawling structure in the center of Tokyo, started to rock. It was 2:46 p.m. All eyes rose to the huge crystal chandeliers above, clinking and shaking violently. "Everyone, please stay in a safe position," committee chairman Yosuke Tsuruho said, grasping the armrests of his upholstered velvet chair. "Please duck under your desk."

Within four minutes, a crisis headquarters was up and running across the street in the prime minister's office. Kan rushed there as soon as the shaking subsided. At 3:37 p.m. he convened a roundtable of his top advisers. Soon after the tsunami hit, Kan's task force was deluged by reports of massive damage up and down the coast, aerial photos and video showing entire villages gone.

Then the Tsunami

The first large tsunami waves struck the coast of northern Japan between 15 minutes and 30 minutes after the earthquake, with coastal areas closest to the quake epicenter being struck first. Waves as high as 12 meters surged onto shore, carrying away cars and boats, setting buildings ablaze and inundating factories, fields and highways. Towering lines of wave uprooted trees, rushed over sea walls trees, ripped down houses and pushed all the debris inland and then pull it back into the sea, leaving behind bits and pieces of this and that and layer of black mud. [Source: New York Times]

Tsunami waves of over 30 meters high were recorded in places where 10-meter waves were pushed higher by narrow inlets and mountains close to the shore. In some of these places houses and even evacuation centers that were supposed to be safe because they were high off the ground were swept away. In other placed the waves swept inland for many kilometers.

The tsunami that struck northern Japan was one of the largest ever recorded and far bigger than scientists thought possible because they did not anticipate such a large earthquake. Researchers at the University of Tokyo estimated that the tsunami wave that struck the Taro District of Miyako in Iwate Prefecture was 37.9 meters in height based on the drift displacement of the port and discovery of lumber from the port on the slope of a mountain 200 meters from the coast. Researchers also found fire engines and fishing boats on the mountain slope. The tsunami waves were so big they destroyed many tidal gauges used to measure wave size. [Source: Kyodo]

Television images showed waves and floodwaters, engorged with floating debris surging inland, pushing aside heavy trucks as if they were toys, depositing buses on four-story buildings ramming fighter jets into houses. Kyodo News reported a gigantic wave sweeping up a ship carrying more than 100 people. “The spectacle was all the more remarkable for being carried live on television,” the New York Times said, “even as the waves engulfed flat farmland that offered no resistance. The tsunami could be seen scooping up every vessel in the ocean off Sendai, and churning everything inland.” [New York Times]

Satellite images revealed how the coastline was changed during the tsunami. Amateur video captured boats being carried down city streets, water rushing through Sendai airport and masses of cars bobbing up and down like rubber ducks in cascades of black water. Shocked observers watched as the water carried away everything in its path.”The tsunami roared over embankments in Sendai city, washing cars, houses and farm equipment inland before reversing directions and carrying them out to sea,” Japanese engineer, Kit Miyamoto, said. “Flames shot from some of the houses, probably because of burst gas pipes.” [Ibid]

The tsunami lasted for two days, as its waves reached as far as Chile before reflecting back towards Japan . By the morning after the tsunami, Japan was filled with scenes of desperation, as stranded survivors called for help and rescuers searched for people buried in the rubble. Several coastal towns were literally wiped off the face of the earth.

Evan Osnos wrote in The New Yorker, “The afternoon of Friday, March 11th, was cool and partly cloudy on the northeast coast of Japan’s main island, a serene stretch once known as the nation’s “back roads.” At 2:46 P.M., as schools were beginning to let out, the ground began to shake. It was violent even by Japan’s standards---the thundering went on for five minutes---and before long Japanese television was warning of a wave charging west across the Pacific Ocean at the speed of a jet. Kicked up from the seabed, the tsunami amplified in size and slowed in speed as it moved into the shallows beside the Japanese coastline, and by the time it touched land it was a wall of water, black and smooth. It was as tall in places as a three-story building, moving at fifty miles per hour. [Source: Evan Osnos, The New Yorker, March 28, 2011]

“Unlike the Indian Ocean tsunami of 2004, the horrific grandeur of this moment unfolded before the unblinking eyes of Japan’s ubiquitous surveillance cameras, mobile phones, and hovering news helicopters, compiling a record of rebuke to the sense of protection once extended by the technology and engineering at the heart of Japanese life.” The tsunami “flicked fishing trawlers over seawalls, crunched them against bridges. It sent fleets of cars and trucks hurtling from parking lots, and turned homes into chips of wood and tile, before heading deeper into Miyagi and Iwate Prefectures across a span of six miles. Rampaging through former farming and fishing villages, and the cosmopolitan city of Sendai, the wave slowed, but remained too fast for most people to outrun on foot. [Ibid]

Tsunamis reached Tokyo but they were small. The first wave to reach Tokyo Bay was about 80 centimeters high. It arrived at 4:40pm about an hour and 45 minutes after the earthquake. The highest was 1.5 meters and came at 7:16 p.m.

Five Million Stranded in the Tokyo Area after the Earthquake

Around 5.15 million people had trouble getting home after the earthquake in Tokyo, Kanagawa, Chiba, Saitama and Ibaraki prefectures, the Japan Meteorological Agency reported.The estimate is based on the results of a survey in which about 5,400 residents in the area were asked how they responded to the situation that day. [Source: Yomiuri Shimbun, November 25, 2011]

The Cabinet Office estimated 3.52 million people were unable to return home in Tokyo; 670,000 in Kanagawa Prefecture; 520,000 in Chiba Prefecture; 330,000 in Saitama Prefecture; and 100,000 in Ibaraki Prefecture. The estimate was reported to a meeting of a panel comprising officials from the Cabinet Office, the Tokyo metropolitan government and a number of companies to discuss measures to help a large number of people who would be stranded if a major epicentral earthquake struck the capital.

Air Controllers Safely Guided Planes after March Quake

A total of 86 flights heading for Haneda and Narita airports when the March 2011 Great East Japan Earthquake struck landed safely, mainly at alternative airports, thanks to the dedicated efforts of air controllers. Jiji press reported: All runways at the two major Tokyo airports were closed soon after the magnitude-9 quake occurred at 2:46 p.m. on March 11 last year, forcing most of the 86 flights to change their destinations. But the planes experienced no accidents or other major problems amid the unprecedented situation. All four of Haneda's runways were reopened by 3:55 p.m. the same day, according to the Land, Infrastructure, Transport and Tourism Ministry. [Source: Jiji Press, April 3, 2012]

But the number of incoming flights the airport could accept was limited, as railway services from the airport were suspended due to the quake and passengers who were there at the time of the disaster were unable to leave, filling the airport's terminal buildings with crowds. Narita Airport remained closed until late at night as passengers and others took shelter on the airport's aprons.

Of the 86 flights, 70 were heading for Narita when the temblor struck, and most of them had designated Haneda as an alternate airport for landing in case of emergencies. The remaining 16 flights were bound for Haneda, and similarly, most of them had been supposed to use Narita as an alternative landing site. But when both Haneda and Narita were shut down after the quake that ravaged northeastern Japan, the 86 planes had to look for different landing sites.

When the earthquake occurred, about 70 air controllers were at the transport ministry's Tokyo Area Control Center in Tokorozawa, Saitama Prefecture. Fortunately, on March 10, the day before the quake, all of them had participated in an annual training program assuming a closure of Haneda runways. Immediately after the quake, about 30 other air controllers joined the original 70, and they contacted the air control management center in Fukuoka to find out if there were any airports where runways and aprons could be used for landing and parking. Such information was conveyed to air controllers who were contacting the crew of the 86 flights through the integrated en-route control system (IECS).

Using the IECS, the air controllers checked remaining fuel and the number of passengers on the planes. As a result, 14 airplanes, mainly from North America, were allowed to land ahead of others because their captains declared emergencies after finding that their planes would not be able to fly much longer. By 8:48 p.m. on March 11, the 86 flights had landed at 13 airports. Of them, 21 landed at Kansai airport near Osaka, 17 at Centrair airport in Aichi Prefecture, and 14 at New Chitose airport in Hokkaido.

Soil Liquefaction Damage After the March 2011 Earthquake

Liquefaction is a phenomenon where pockets of stable sand underground are shaken by an earthquake and mixed with groundwater. As a result, the soil becomes sludgy and unstable. In some cases, muddy water reaches the surface. Because the ground foundation suddenly becomes soft, buildings may sink or tilt. Tilted houses, rippled pavement, broken pipes are all problems associated with liquefaction. [Source: Akio Oikawa and Shogo Hara, Yomiuri Shimbun , October 18, 2012]

The Japan Meteorological Agency reported that liquefaction occurred in 184 locations in 96 cities wards, towns and villages in Tokyo and six prefectures (data unavailable in coastal regions hit by the tsunami). According to a Yomiuri Shimbun survey: “Damage to homes from soil liquefaction caused by the Great East Japan Earthquake was not limited to the three worst-hit prefectures in the Tohoku region but also spreads across six prefectures in the Kanto region. In addition to the Tohoku prefectures of Iwate, Miyagi and Fukushima, Tokyo and five prefectures--Ibaraki, Chiba, Saitama, Kanagawa and Tochigi--suffered damage from liquefaction.” [Source: Yomiuri Shimbun, July 5, 2011]

“There were at least 23,700 cases of damage to houses, including those suspected to have been caused by liquefaction. Chiba Prefecture has the largest number: about 18,400 cases, including many in Urayasu. Ibaraki Prefecture had about 5,100 cases. The majority of damage in inland areas was believed to have occurred on land reclaimed from bogs and paddies. Damage in areas along the Tonegawa river was especially noteworthy.” [Ibid]

Houses that look outwardly normal have sunk or become uneven. Repairs are costly and residents have experienced symptoms of ill health, including dizziness. Many have also expressed fear of further liquefaction as a result of aftershocks. In a typical case The first floor of the wooden two-story house of a 45-year-old company employee in the Minami-Kurihashi district in the city is slanted, with its highest point now 20 centimeters above the lowest. The man consulted a building constructor, who said it would cost about ¥10 million ($120,000) to lift the house by putting steel pipes underneath it. The cost of fixing another house that had sunk to such a degree the water and sewage system didn’t work was ¥12 million. [Ibid]

About 9,000 residential buildings were damaged by the liquefaction from the March 2011 earthquake in Urayasu, Chiba Prefecture. Reconstruction was slow. A year and half after the disaster tilted houses still remain, and ripples remain in some roads in the area. It will take about three years for the water supply and sewerage systems to be fully restored. [Source: Akio Oikawa and Shogo Hara, Yomiuri Shimbun , October 18, 2012]

In some places, houses sank into the ground and sewer pipes under roads were clogged. Yuko Shiina, a 47-year-old homemaker, relies on makeshift pumps set up by the city government to keep the sewers flowing. She said: "Under usual conditions there is no problem at all. But this summer, I worried about what I would do if the pumps stopped due to a blackout or an electric power shortage.”

Most of Urayasu is reclaimed land. In one extreme case, a building sank nearly 90 centimeters into the ground. Among about 9,000 buildings damaged by the disaster, about 1,400 are severely damaged houses, qualifying the owners to receive subsidies from the central government. [Ibid]

March 2011 Earthquake Causes Dam to Collapse

In the Naganuma district of Sukagawa, in an inland part of Fukushima Prefecture, the earthquake caused Lake Fujinuma agricultural dam to collapse which turn caused muddy water to inundate a residential area downstream, leaving seven people dead and a 1-year-old boy missing. Water from the dam flooded an area of 86.7 hectares downstream, causing serious damage to the inland area. Nineteen houses were totally destroyed, while 55 more were flooded to varying degrees. Fifty-six survivors from 15 households are now living at evacuation centers. [Source: Yomiuri Shimbun, June 1, 2011]

On March 11, immediately after the earthquake, Katsutoshi Shishido told the Yomiuri Shimbun he saw that the 18-meter-high, 133-meter-wide dam was collapsing. "There was such a roar that I could hardly understand what was going on," Shishido, 72, said. Water escaping from the dam, which had a storage capacity of 1.5 million tons, became a muddy torrent that hit the Taki area, about one kilometer downstream. [Ibid]

From a window on the first floor of her house, Mitsuko Nakamura, 65, saw a five- to 10-meter-high flood approaching. She grabbed her two grandchildren, aged 2 and 4, and dashed up to the second floor. The three waited, shivering from cold until the water receded. "I never expected my house to be destroyed by dam water," Nakamura said. [Ibid]

The victims range in age from 14 to 89. Moeko Hayashi, 14, was found dead in the Abukumagawa river in Nihonmatsu, about 40 kilometers downstream from the Taki area, on April 24. She had been missing since the dam collapsed 44 days earlier. When Hayashi, a second-year student at Naganuma Middle School, was swept away, she was at her grandfather's house with her mother. Hayashi and her mother tried to hold hands, but the roiling water pulled them apart. Only the mother was rescued after reaching the riverbank. [Ibid]

The dam was built in October 1949 to secure an agricultural water supply to downstream areas that had suffered a water shortage. The earthfill dam was built as an embankment with a trapezoidal cross-section to hold water back. "The sloped surface collapsed like a landslide due to the earthquake, and then--because of the water pressure--the dam gave way at once," Seiki Kawagoe, an associate professor at Fukushima University, told the Yomiuri Shimbun. Kawagoe specializes in natural disaster science. He examined the site of the dam after its collapse. [Ibid]

The core of the dam was reinforced with concrete blocks. From 1984 to 1992, liquid cement was injected into it to prevent water leakage. Kawagoe said, "When a dam's foundation is weak, it's difficult to maintain its structural strength despite repeated reinforcement." "It is necessary to inspect the dam thoroughly. For example, rigorous research of cracks inside the construction, which cannot be seen from outside, should be carried out," he added. [Ibid]

Aftershocks After the March 11 Earthquake

There were hundreds of aftershocks after the main March 11 earthquake---over 600 by one count in the first week after the main quake---many equivalent to major quakes that would have killed hundreds if they were in a different country. Immediately after the main quake at 2:46pm a 7.0 aftershock hit coastal areas of Iwate Prefecture at 3:08pm, followed by another at 3:15 off Ibaraki Prefecture that measured 7.4 on the Richter scale. This was in addition to a 7.2 earthquake that struck the region a week before the main March 10 quake.

The U.S. Geological Survey reported dozens of additional aftershocks off the coast of Honshu Island on the day of the main quake. Just after 10 p.m. local time, a 6.4 magnitude aftershock hit 50 miles away from Fukushima Prefecture, shaking buildings as far away as Tokyo. The U.S. Geological Survey recorded 96 aftershocks on the Sunday, two days after the main quake, and many Japanese were alarmed at several earthquake warnings that appeared as televised bulletins on Monday. A warning at 4 p.m., an alert announced by gentle trilling bells told of expected ''strong shaking'' across the entire waist of Japan, essentially from Tokyo to Kyoto. A total of 539 aftershocks struck Japan in the week after the quake. An American informed his Twitter followers: “I’m no longer going to tweet aftershocks below M5.0---they’ve just become too frequent.” On top of that a 7.2-magnitude quake had hit Japan just two days before the main quake and tsunami .

A total of 232 aftershocks measuring 4 or stronger on the Japanese seismic scale were recorded as of March 2012. As time went by the number of aftershocks decreased and the scale of the tremors weakened. However, the Meteorological Agency warns that “the largest aftershocks tends to be smaller than the main quake only by about a magnitude of 1. Therefore, it would not be unusual for a magnitude-8 class aftershock to occur, since the main quake was magnitude-9. Meanwhile, earthquakes in locations distant from the focus of the March 11 great quake have been increasing in frequency. This situation reportedly is due to changes in the way the Earth's forces have affected the tectonic plates since the great quake. So, a large threat is now posed by epicentral quakes in inland areas.” [Ibid]

Large Aftershocks After March 2011 Earthquake and Tsunami

As of April 27 2011, there had been 435 aftershocks with a magnitude of 5 or greater and 11 with a magnitude 7.0 or greater. This is the largest number of aftershocks in Japan’s history. Experts say there are more shocks to come, possibly as strong as magnitude 8. The Japanese Meteorological Agency warned, "Earthquakes have come to occur frequently as the geological dynamics of eastern Japan have changed due to the March 11 earthquake...We have to expect more earthquakes in the magnitude-7.0 class for the time being.”[Source: Yomiuri Shimbun, April 14, 30 2011]

On April 8, an aftershock that measured 7.1 on the Richter scale struck northern Japan, killing three, injuring 132 and bring more hardship to people already suffering a lot. Already damaged houses shook on their foundations and people that just had their electricity, gas and water restored after having lost them for weeks lost them again. No further damage was reported at nuclear power plants in the region. Another 7.1-magnitude quake struck the Fukushima area---where the nuclear power plant is located---on April 11. According to the U.S. Geological Survey this aftershock struck 38 kilometers west if Iwaki, Fukushima, Province at a depth of 13 kilometers.

On April 12, a magnitude-5.6 earthquake occurred in northern Nagano Prefecture, while on the same day a magnitude-6.4 earthquake struck offshore from eastern Chiba Prefecture. Nagano is in the mountains west of Tokyo, relatively far from the March 11 quake. On March 12, northern Nagano was jolted by a magnitude-6.7 earthquake whose focus was 20 kilometers north of the April 11 earthquake.

On June 24, a magnitude-6.7 earthquake---an apparent aftershock from the magnitude 9.0 megaquake on March 11--- jolted Aomori and Iwate prefectures but did not spawn significant tsunami, the Meteorological Agency said. The agency issued Iwate Prefecture a warning for tsunami of up to 50 cm immediately after the 6:51 a.m. quake but lifted it at 7:45 a.m. There were no immediate reports of injuries or damage from the quake, which registered lower 5 on the Japanese seismic intensity scale to 7 in the town of Hashikami, Aomori Prefecture, and in northern areas of Iwate Prefecture, including the city of Morioka. Nuclear power stations in the area also escaped damage, including the crisis-hit Fukushima No. 1 nuclear plant in Fukushima Prefecture, the Higashidori plant, a reprocessing plant for radioactive waste in Aomori Prefecture, and the Onagawa plant in Miyagi Prefecture, the Nuclear and Industrial Safety Agency said. East Japan Railways Co. said the Tohoku Shinkansen Line was temporarily suspended between Ichinoseki and Shinaomori stations, affecting some 600 people. [Source: Kyodo, June 24, 2011]

High Tides Flooding Quake-Sunk Land After the March 2011 Earthquake and Tsunami

In May 2011 the Yomiuri Shimbun reported: “Flooding has been a regular occurrence in some neighborhoods in Ishinomaki recently, but it has nothing to do with torrential rains--high tides now inundate land that was sunk by the Great East Japan Earthquake. The seawater floods have forced residents to leave their homes and a local primary school to change its schedule so children would not be stranded at school by the rising waters. In one area of the city, waters were about one meter deep during the spring tides.”

Kazunori Akiyama wore fishing waders and walked through knee-deep water to pick up a parcel from a customer in the Shiotomicho district of the city. Carrying the box on his shoulder, the 38-year-old delivery company employee said, "The water's unavoidable during deliveries at this hour. I have to be careful with people's packages to keep them dry."

According to the city government, some areas sank by as much as 78 centimeters due to the disaster. About 300 households in Shiotomicho, Mangokucho and other districts now flood regularly. Residents have asked the city government to provide sandbags to protect their homes.

Mangokuura Primary School has had to be flexible to make sure its 417 students are able to make it home before high tides block off roads. Kids are let out three hours before high tide, meaning school sometimes ends as early as 1 p.m. Floods have also hindered ambulances trying to respond to emergencies in the city.

Ishinomaki Mayor Hiroshi Kameyama went to the Miyagi prefectural office Wednesday to ask for emergency aid to cope with the flooding during high tides. The prefectural government decided to erect a temporary embankment and set up drainage pumps along the coast in two districts by early June. But a city government official warned, "When the rainy season comes, there could be some major flooding when the rains combine with high tides."

Videos of the Tsunami

Collections of Tsunami Video

Collection of Videos of the 2011 Tsunami

Collection of videos of the 2011 Tsunami

Collection of Videos

Video of Geology of 2011 Tsunami

Geology of 2011 Tsunami

Video of Tsunami Waves and Whirlpools

View of Tsunami from Ship at Sea

Tsunami Whirlpool

Video of Tsunamis Waves Come Ashore

Tsunami Comes Ashore

Helicopter Shot of Waves Coming Ashore and Devastating Land

Tsunami Overcomes Sea Wall

Ground Level Footage of Tsunami

Wave Coming in Oirase

Video of Boats and Cars Tossed by the Tsunami

Boats Crashing Ashore in Sendai

Tsunami Smashes a Boat

Tsunami Hits Parking Lot and Cargo Area, Carry Away Ships
Strike Sendai Airport

Video of Tsunamis Hitting Towns

Black Tsunami Goes Over Wall in Miyako

Tsunami Comes Ashore in Miyako

Tsunami and Fire, Tsunami Spread on Land

Tsunami Hits Aomori

Tsunami Smashes Through the Middle of a Town in Iwate

Tsunami Rushes Up a River

Earthquake and Tsunami Through Middle of Town

Video of Tsunami Hitting Sendai Area

Helicopter Shots of Fire and Damage in Sendai

Refinery Fire in Ichihara

Image Sources: 1) U.S. Navy; 2) United States Geological Survey USGS); 3) National Oceanic and Atmospheric Administration (NOAA); 4) NASA; 5) U.S. Marines

Text Sources: New York Times, Yomiuri Shimbun, Daily Yomiuri, Washington Post, Los Angeles Times, Kyodo News, National Geographic, The Guardian. Times of London, The New Yorker, Time, Newsweek, Reuters, AP, AFP, and various books and other publications.

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© 2008 Jeffrey Hays

Last updated January 2014

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