TSUNAMI PREPAREDNESS IN JAPAN
tsunami refuge In some coastal towns such as Kamaishi on northeastern Honshu schools conduct disaster drills to go uphill, teach tsunami velocity calculations in math class and discuss tsunami experiences during ethics lessons. Schools also encourage students to look for higher ground where they can evacuate on foot, and include evacuation routes in a disaster management map.[Source: Sho Komine, Yasushi Kaneko, Yomiuri Shimbun , March 29, 2011]
Children in the region struck by the earthquake and tsunami in 2011 were taught “tendenko” “which means “go uphill independently at the time of Dynasty caring only for your own safety, not thinking of anyone else, even your family.” One 12-year-old survivor of the 2011 tsunami told the Yomiuri Shimbun, “I was worried about my house and family, but I ran up to a higher place without thinking.” Tendenko became part of local psyche of northeastern Honshu, according to Prof. Toshitaka Katada of Gunma University, after the 1896 Sanriku earthquake when many died because they were trying to help family members when the tsunami struck.
Katada told the Yomiuri Shimbun: “You might feel bad escaping a tsunami alone. However, trying to conform families’ safety and whereabouts is the most dangerous thing one can do in such as a situation. It’s important that you mutually believe that, “They must’ve evacuated somewhere.”
James Glanz and Norimitsu Onishi, New York Times,” Especially in the 1980s and 1990s, built concrete seawalls in many communities, some as high as 40 feet, which amounted to its first line of defense against the water. In some coastal towns, in the event of an earthquake, networks of sensors are set up to set off alarms in individual residences and automatically shut down floodgates to prevent waves from surging upriver...In one town, Ofunato, which was struck by a major tsunami in 1960, dozens of signs in Japanese and English mark escape routes, and emergency sirens are tested three times a day. [Source: James Glanz and Norimitsu Onishi, New York Times, March 11, 2011]
“Critics of the seawalls say they are eyesores and bad for the environment. The seawalls, they say, can instill a false sense of security among coastal residents and discourage them from participating in regular evacuation drills. Moreover, by literally cutting residents’ visibility of the ocean, the seawalls reduce their ability to understand the sea by observing wave patterns, critics say.”
Loudspeakers dangle from lampposts, ready to broadcast warnings that a wave is coming and everyone must run for higher ground.
As the earthquake and tsunami in 2011 showed these measures were not enough. Experts say that Japan needs to build houses and hospitals and transportation lines further back from the coast; plant more pine trees and mangroves to slow tsunamis down; and build more evacuation centers that can withstand the waves. Fumihko Imamura, a professor at the Tohoku University Disaster Control Research Center told Reuters: “We’re living very close to the coast. The fishing industry needs to be near the coast, but living areas and other facilities need to be farther in...We need land-use planning. “
Good Websites and Sources: Wikipedia article on Tsunamis Wikipedia ; Surviving a Tsunami, Lessons from Chile, Hawaii and Japan pubs.usgs.gov ; Tsunami Warning System in Japan jma.go.jp/jma ; Tsunami Warnings from Japan Meteorological Agency jma.go.jp/en/tsunami ; Book: “Tsunami: The Underrated Hazard” by Edward Bryant. Tsunamis That Struck Japan Major Tsunamis in Japan in the 20th Century tsunami.civil.tohoku.ac.jp ; Major Earthquakes and Tsunamis in Japan in the 20th Century drgeorgepc.com ; 1933 Earthquake and Tsunami pdf file cidbimena.desastres.hn ; 1983 Tsunami drgeorgepc.com ; Report on the 1993 Tsunami nctr.pmel.noaa.gov ; Small Tsunami in 2010 reuters.com
Preparing for a Once in 1,000 Years 'Calamity’
Fumihiko Imamura, the director of the Disaster Control Research Center of Tohoku University, said after viewing the damage of the March 2011 earthquake and tsunami: "We must think seriously of how to face the risk of an 'extremely low- probability calamity,' and how to hand down lessons learned for posterity." [Source: Yomiuri Shimbun, January 18, 2012]
The recent period of high economic growth, which enabled Japan's "miraculous" economic recovery and development, happened to occur during a phase of few large-scale natural disasters in the archipelago's history, according to some experts. The fact that many industries and groups of people could gather in places such as Tokyo and the Tokai region, which are vulnerable to natural disasters, may have been thanks to such good luck. With the unprecedented Great East Japan Earthquake and accident at the Fukushima No. 1 nuclear power plant, the question now is how to prepare for and prevent damage from disasters.
How much should we prepare for extremely rare disasters said to occur once every 1,000 years? And what about recent extreme weather conditions in which conventional wisdom cannot work? During the Great East Japan Earthquake, the height of coastal seawalls affected the fates of those hit by the tsunami.
The tsunami overran an about 10 meter-high seawall in the Taro district of Miyako, Iwate Prefecture. However, a seawall measuring more than 15 meters high in the village of Fudai and another 12 meter-high seawall in the town of Hirono stopped the waves. The seawall in the Taro district, which was completed in 1978, cost more than 400 million yen in total. The Fudai seawall, completed in 1984, cost 3.5 billion yen. The cost of a bay mouth seawall in Kamaishi Port, which was destroyed by the tsunami, cost 120 billion yen. It is true that the higher the seawalls, the better. But a tsunami more than 15 meters high could hit in certain areas. Considering costs, it is impossible to make seawalls high enough to block every possible tsunami.
Former Fukuoka Gov. Wataru Aso, who served as president of the National Governors' Association, said: "It's impossible to take disaster management measures by assuming [it will be] the one that takes place once every 1,000 years. "The cost is unimaginable. I think 'software,' such as evacuation drills, are more important than 'hardware.'" In fact, experts said municipalities that practiced such drills and other "software" measures suffered less damage from the March 11 disaster.
Experts are paying more attention to this extremely rare type of disaster. For instance, once every 10,000 years or so, large volcanoes may have "catastrophic eruptions," the likes of which have not been witnessed by civilizations for thousands of years. Should this type of disaster occur, it could ruin not only a nation, but the entire planet. Experts at the Volcanological Society of Japan have begun holding symposiums with government officials to assess such risks. A magnitude-5.8 earthquake in the eastern United States, the first since the late 19th century, occurred in August. The quake caused a nuclear power plant in Virginia to automatically stop, leading to demands from U.S. experts for measures against extremely rare earthquakes.
Floodgates, Seawalls and Other Tsunami Protection
Structures designed to prevent the influx of high water from the sea include sea walls, embankments and other barriers. Floodgates are set up across rivers or canals to halt surges of water. Many sea walls have movable gates to enable people and vehicles to pass through a seawall. Seawall gates in the coastal areas are four to six meters higher than water levels at full tide. Some are closed by remote control. Others are closed manually by fire departments and sometimes private-sector companies.
There are 44 floodgates and 46 seawall gates on Tokyo Bay that were built to protect Tokyo from tsunamis, typhoons and tidal surges. After the March 2011 earthquake authorities failed to close six floodgates and seawall gates before the first tsunami arrived on the Tokyo Bay coast the Yomiuri Shimbun revealed.
Japanese dam builder Hitachi Zosen has developed a seawater barrier that deploys automatically when tsunami waves approach shorelines.The Neo Rise barrier is a form of floodgate designed to prevent damage from tsunamis, floods, and storm surges brought on by typhoons. It's based on Hitachi's air-powered flap gates, which lie at the bottom of harbors and close them off in the event of a major change in sea level. [Source: Tim Hornyak, CNET Asia, June 11, 2010]
Neo Rise (from "no energy, no operation, rising seawall") is set up on land. It runs on hydraulic power associated with riding tides and closes automatically, protecting shoreline communities; it can also be operated manually. It's designed as simply as possible to avoid mechanical failures and high maintenance costs, according to Hitachi.
Miyako Seawall Height to Be Raised to 14.7 Meters
In October 2011, the Yomiuri Shimbun reported: “The Iwate prefectural government plans to increase the height of the huge seawalls in the Taro district of Miyako, Iwate Prefecture, as it repairs the damage from the massive March 11 tsunami, it has been learned. The set of two intersecting seawalls, dubbed the "Great Wall" after China's famous structure, will be raised by 4.7 meters to 14.7 meters, an official said, adding it will take five years to complete the expansion project. [Source: Yomiuri Shimbun, October 25, 2011]
The planned height is lower than the 16.3 meters recorded by the devastating tsunami that followed the magnitude-9.0 earthquake. Instead of relying merely on seawalls, the Miyako municipal government will take multiple approaches to safeguard residents against disaster, the official said.
In the Taro district, many residents were killed in the 1896 Meiji Sanriku Earthquake and the 1933 Showa Sanriku Earthquake. Given the huge number of casualties, a seawall building project was launched in 1934. The walls, 10 meters high and totaling 2.4 kilometers in length, were completed 44 years later, in 1978.
The district reported no victims in the tsunami caused by the 1960 Great Chilean Earthquake thanks to the construction, which had been partly completed by then. This time, however, the tsunami destroyed a 528-meter portion of seawall near the coast, leveling it to its foundations. Walls further inland remained intact, but the tsunami surged over them, leaving 179 people dead and six others missing. The largest tsunami ever recorded in the district is said to have reached a maximum height of 21 meters, occurring in 1611 following the Keicho Sanriku Earthquake.
Determining the frequency of such enormous tsunami as low, the prefectural government has decided to raise the walls' height to 14.7 meters--higher than the 14.6 meters and 10.1 meters recorded, respectively, in the Meiji Sanriku Earthquake and the Showa Sanriku Earthquake--to protect against tsunami triggered by earthquakes that could happen at intervals of several decades or 100-plus years, the official said.
According to a survey conducted by the Miyako municipal government, more than half of the 560 respondents favored moving to high ground or out of the city. The municipal government has been holding talks with residents and presenting four proposals, including moving to high ground and land elevation. "We have relied too much on seawalls until now," said Miyako Mayor Masanori Yamamoto. "We want to work toward building a community with multiple disaster-response capabilities by expanding evacuation routes and carrying out sufficient antidisaster drills."
New Remote Control Floodgate System
As part of its tsunami safety measures, the Yomiuri Shimbun reported, Japan’s infrastructure ministry has decided to introduce a remote control system for all the floodgates on major rivers emptying into the Pacific Ocean. The system is designed to safely and securely close the floodgates of Class 1 rivers when there is a risk of a tsunami flowing upstream in the aftermath of a major earthquake. [Source: Yomiuri Shimbun, October 31 2011]
The system was devised in response to the fact that more than 70 volunteer firefighters in charge of closing floodgates or seawall gates were killed or went missing in the massive tsunami that hit the Pacific coast in the Tohoku region following the devastating Great East Japan Earthquake on March 11. The Land, Infrastructure, Transport and Tourism ministry has earmarked about ¥7.7 billion yen, including the cost of installing remote control systems, in the third supplementary budget for the current fiscal year ending next March, to implement tsunami control measures for the nation's rivers.
The system will first be introduced for rivers along the Pacific coast where the major tokai, Tonankai and Nankai earthquakes are anticipated, and where several large cities are located. Class 1 rivers on the coast are equipped with 188 floodgates in total. Of these rivers, 62, including those on the Arakawa and Yodogawa rivers in Tokyo, have already adopted a remote control system for opening and closing operations via personal computers and other systems, the ministry said.
The remaining 126 floodgates of such major rivers as the Tonegawa, Kisogawa and Shimantogawa have yet to introduce the system due to high installation costs, the ministry said, meaning firefighters have to go to the floodgates in person, fully aware of the danger they face. It costs tens of millions of yen to install a remotely controlled floodgate.
About 70 percent of the 108 students at Okawa Primary School in Ishinomaki, Miyagi Prefecture, were killed or went missing after being swept away by tsunami flowing upstream on the Kitakamigawa as they tried to evacuate to high ground from the school located along the river. As this incident clearly shows, closing floodgates is an important disaster-response measure.
The ministry also plans to promote a system to automatically switch to reserve electricity sources when the power supply to floodgates is cut. The plan also calls for adopting waterproof and earthquake-resistant measures for the reserve power system, such as installing such facilities on high ground.
According to the Land, Infrastructure, Transport and Tourism Ministry, there were 25,463 floodgates and seawall gates at least two meters wide at seaports and elsewhere across the country as of March last year. Of these, just 742 units, or about 3 percent, could be remotely controlled, the ministry said.
The ministry will ask each prefecture to increase the number of remotely controlled floodgates and seawall gates while inspecting how the gates have been used and administered. Based on its findings, the ministry will decide on the order in which gates should be closed after an earthquake, and study a plan to keep shut at ordinary times gates that do not need to remain open.
Coastal Forests Provide Powerful Defense Against Tsunamis
Research by the Japanese Forestry Agency has shown that coastal forests provided defense against the March 2011 tsunami acting as "natural levees."Disaster-prevention forests are defined by the Forest Law as belts of trees, such as Japanese black pines, planted in coastal areas to prevent damage from wind, airborne sand and tsunami. Historians say trees have been planted for such purposes since the Edo period (1603-1867). Currently, disaster-prevention forest belts exist on about 3,300 kilometers of the nation's coastlines. [Source: Yomiuri Shimbun, October 7, 2011]
Tadashi Shoji, 75, the head of a neighborhood association in Wakabayashi Ward, Sendai, said, "If it wasn't for the disaster-prevention forests, the damage here [from the March 11 tsunami] could have been much more serious." The city's coastal areas were struck by waves about seven meters high on March 11, but the waves were just 40 centimeters high by the time they reached Soji's neighborhood, which is located behind the forests.
The water level in Shoji's house did not rise above floor. No one in the neighborhood was killed by the tsunami, Shoji said. In Iwate and Fukushima prefectures, there were about 10 cases in which forests prevented cars and ships that had been swept up by tsunami from being carried into residential areas.In contrast, areas near port facilities and other places without protection from forests suffered much greater damage.
Research conducted by the Forestry and Forest Products Research Institute in Ibaraki Prefecture on behalf of the agency found strong evidence of how disaster-prevention forests can alleviate tsunami damage. The research found that if tsunami 16 meters high hit a coastal town with no forest protection, the water would continue traveling inland at a speed of about 10 meters per second, and cover 600 meters in about 18 minutes. If the town did have forest protection, the waves would travel inland at just two meters per second, and take about 24 minutes to reach a point 600 meters inland.
The March 2011 tsunami triggered by the Great East Japan Earthquake damaged about 3,660 hectares of forest. Prior to March 11, the Pacific coastlines of Aomori, Iwate, Miyagi, Fukushima, Ibaraki and Chiba prefectures had a total of about 230 kilometers of disaster-prevention forests. The disaster swept away about 160 kilometers, or two-thirds.
Some of the trees were not planted in places where they could develop deep root systems, which reduced their ability to resist tsunami.The agency has conducted research on how and where to plant trees to increase their resistance to tsunami, so that the new forests will act like natural levees. To help allow roots to extend deeper, the agency plans to raise the ground along the coast by three to five meters before planting the trees. Debris from the disaster will be used to help raise the ground level. The agency intends to make all stretches of disaster-prevention forest about 200 meters wide, up from about 50 to 100 meters before the disaster.
Tsunami Evacuation Centers
Many people were able to survive the tsunami by taking shelter in specially designated tsunami evacuation buildings — buildings where people evacuate during tsunami when higher ground is not available. Municipal governments designate buildings that are likely to withstand a major earthquake or tsunami. Some of these buildings are schools or other public facilities. In other cases, requests are made to owners of condominiums or other buildings. Three- to four-story or taller buildings are chosen so that evacuees will not be engulfed by the tsunami. [Source: Yomiuri Shimbun, September 27, 2011]
The Cabinet Office, a government agency, conducted research in March 2010 and found that 1,790 buildings--mainly in the Tokai and Shikoku regions--were designated as tsunami shelters. But in some regions, no such buildings existed. The Yomiuri Shimbun conducted a survey in August 2011 in 197 cities, towns and villages susceptible to tsunami during the anticipated Tokai, Tonankai or Nankai earthquakes. About 72 municipal governments, or 37 percent of the respondents, reported a shortage of tsunami evacuation buildings. As to why, most respondents said not enough tall buildings existed, while others said automatic locking made using some buildings difficult.
While the municipal governments are trying to increase the number of appropriate tsunami evacuation buildings, it's also important for people to check for themselves where tall buildings and higher grounds exist, and to think about how they plan to evacuate should a tsunami occur.
Tsunami Warnings in Japan
Japan has a fairly sophisticated tsunami warning system. Tsunami alerts are issued in television and radio when large earthquakes occur at sea in the vicinity of Japan. More often than not the warnings turn out to false alarms, sometimes very costly ones that cost millions of dollars in lost productivity if a large area is evacuated.
In November 2006, tsunami warnings were shown repeatedly on television after an 8.1 earthquake occurred in the Russian-held islands north of Hokkaido. The tsunamis ended up being only a 40 or 50 centimeters high at their highest and few people — even those living in area deemed most dangerous — heeded the warnings and headed for higher ground or shelters. A larger tsunami generated by the same earthquake traveled clear across the North Pacific and produce a 1.8 wave in California and damaged docks and overturned one boat.
In January 2007, an 8.2 earthquake occurred off the coast of Hokkaido about 100 kilometers from the spot 7.9 earthquake occurred in November 2006. . tens of thousands of residents were ordered to seek higher ground in the event of a tsunami. Tsunami warning were issued on television and radio but were widely ignored. The tsunami that hot Hokkaido was only around 20 centimeters high at its highest. It was predicted to be a meter high.
Japan’s Tsunami Warning System
The Meteorological Agency’s tsunami warnings predict where a tsunami will hit, when it will arrive and its height, Takashi Ito wrote in the Yomiuri Shimbun. For purposes of specifying locations, the agency divides the nation's coastline into 66 segments. Warnings can be issued within about three minutes of an earthquake occurring, quicker than any other tsunami alert system in the world. [Source: Takashi Ito, Yomiuri Shimbun, June 30, 2011]
The process of tsunami prediction begins by calculating the scale of an earthquake and the location of its focus. Based on that data, the agency selects the closest match from 100,000 previously calculated tsunami-pattern projections.
The Japan Meteorological Agency uses the agency’s magnitude scale, or Mj. Under the Mj system, information about a currently occurring earthquake is put into a formula that calculates the predicted consequences of the quake, based on historical data. An advantage of the Mj system is its speed, but its accuracy for earthquakes stronger than magnitude 8 is seriously compromised by the lack of modeling data, because few quakes of such magnitude have occurred in the past. Magnitude 8 is essentially the maximum the Mj formula can handle--even if the earthquake is stronger than that, the formula will base its calculations on a magnitude-8 event.
Failure of Japan’s Tsunami Warning System
Takashi Ito wrote in the Yomiuri Shimbun: “Although tsunami warnings were issued ahead of the giant wave generated by the Great East Japan Earthquake on March 11, more than 20,000 people on the coast of the Tohoku and Kanto regions were killed by or went missing in the water. It would be hard to claim, then, that the tsunami warning system was successful. [Source: Takashi Ito, Yomiuri Shimbun, June 30, 2011]
When the Great East Japan Earthquake struck, the system at first registered its scale as magnitude 7.9 and a tsunami warning was issued, predicting heights of six meters for Miyagi Prefecture and three meters for Iwate and Fukushima prefectures. The agency issued several revisions of the initial warning, increasing its height prediction over a series of updates to "more than 10 meters." However, the revised warnings could not be communicated to many residents because of power outages caused by the earthquake.
Many residents after hearing the initial warning apparently thought, "The tsunami will be three meters high, so it won't come over the protective wave barriers." The error in the initial warning likely was responsible for some residents deciding not to evacuate immediately. The agency itself admits this possibility.
On March 11, the size of the tsunami was underestimated in the first warning because the agency erroneously figured the scale of the earthquake was magnitude 7.9. This figure was later revised to magnitude 9.0.The major reason for the mistake is the agency's use of the Japan Meteorological Agency magnitude scale, or Mj.
Overhauling the Tsunami Warning System
Shortly after March 11, representatives from local governments were openly critical of the agency at a meeting of an expert panel of the Central Disaster Management Council investigating the disaster. Among the improvement measures now being considered by the agency are: introducing a simplified method to more quickly measure the moment magnitude of an earthquake; and applying the highest-level tsunami alert to initial warnings following quakes of magnitude 8 or higher for multiple-quake events such as the anticipated Tokai, Tonankai and Nankai quakes. [Source: Takashi Ito, Yomiuri Shimbun, June 30, 2011]
The Mj system, used to predict the March 2011 tsunami, is fundamentally inappropriate for use in the case of a gigantic quake such as that of March 11. A more accurate way of measuring earthquakes of magnitude 8 or greater is by the "moment magnitude" scale, or Mw. Under this system, an earthquake is measured in terms of the energy released, based on the movement of the fault. However, Mw calculations require "an observation period of at least 10 minutes," according to an official at the agency, which makes it unsuitable for use as the basis of tsunami warnings. "People in this country should be made aware that the actual scale of an earthquake that tops magnitude 8 can't be grasped as quickly [as that of a smaller quake]," the official said.
There are also problems with how the agency's current system makes use of data provided by observations of tsunami already in progress. At present, the agency adjusts tsunami predictions based on fluctuations in the sea surface level measured by Global Positioning System-equipped wave recorder buoys. On March 11, data from the buoys was the basis for revising the warnings about the height of tsunami to more than 10 meters. However, the buoys can be located no more than 20 kilometers from the shore, as that is the maximum range for radio communication to land stations. This presents problems because the 20-kilometer distance to the shore can be quickly covered by tsunami.
Ocean bottom water pressure gauges installed on the ocean floor can provide similar data from locations up to 200 kilometers out to sea. The devices calculate the height of the sea surface based on water pressure, and transmit the data via cable. At present, organizations including the Japan Agency for Marine-Earth Science and Technology have installed such gauges.
On March 11, a pressure gauge on the ocean floor about 70 kilometers off Kamaishi, Iwate Prefecture, detected a tsunami with a height of five meters. Tsunami become taller as they approach land, so considering this data would have made it clear that the wave would be much higher than five meters by the time it reached the coast. The Meteorological Agency intends to make more use of data from ocean bottom pressure gauges in its tsunami warning system. Tsunami prediction methods that are not based on the size of an earthquake are also being studied by the agency. The agency's Meteorological Research Institute and other organs have been developing systems to predict tsunami height by using computer simulations based on data from GPS wave recorders and underwater pressure gauges.
The Meteorological Agency also needs to devise better ways of communicating information to residents. At a study meeting held at the agency in June on improving the tsunami warning system, talk centered on whether warnings should even announce the predicted height of tsunami. Some participants said information on tsunami height is necessary to clearly convey the degree of danger. Others argued that if residents heard a warning about a tsunami but the expected height was relatively low, they would feel misplaced confidence that the tsunami did not pose a serious threat.
Disaster warnings are effective only if they reach residents and motivate them to take appropriate action in response. The tsunami warning system needs to be improved not only in terms of scientific accuracy and technical reliability, but also in its ability to affect the attitudes of the people it is intended to protect.
GPS Tsunami Warning Monitors
Japanese meteorologists will use newly deployed GPS technology to issue tsunami warnings more quickly and accurately for the Japan Sea coast. The land ministry has installed three Global Positioning System-based tsunami monitors off the northern prefectures of Aomori, Akita and Yamagata. The monitors use buoys located about 20 kilometers offshore and radio waves from satellites to detect tidal changes and predict tsunamis before they hit shore. [Source: japan-afterthebigearthquake.blogspot.com October 10, 2011]
The new system, scheduled to start Tuesday, enables the Meteorological Agency to monitor tsunamis in the Japan Sea for the first time. Installation of the technology brings the number of GPS-based tidal monitors in Japan to 15 and the overall number of tsunami monitoring posts to 187. The agency says it hopes the GPS-based systems will help it to provide better tsunami warnings. The agency was able to revise predicted heights of the March 11th tsunami upward based on readings of GPS meters off the Pacific coast.
Wave Radar May Help Tsunami Predictions
Kansai University is developing a a next-generation tsunami prediction system by calculating the estimated height of tsunami when they reach the coast using data obtained through ocean wave radars installed along the coast. Based on lessons learned from the tsunami caused by the Great East Japan Earthquake, the research is aimed at providing more accurate tsunami prediction within five minutes of the occurrence of an earthquake so residents would be able to evacuate quickly. [Source: Yomiuri Shimbun, March 14, 2012]
An ocean wave observation radar system sends radio waves toward the ocean's surface and analyzes the radio waves reflected off of ocean waves, calculating the speed and size of the ocean waves. This radar system is typically used to monitor tidal currents. In the case of the March 11 earthquake, it was discovered that an ocean wave radar system installed by the land ministry in Wakayama Prefecture detected the tsunami about 30 kilometers off the coast. Prof. Tomoyuki Takahashi of Kansai University noted this discovery. Under the planned project, the radar system will be installed at two locations along the coast of the prefecture to monitor the ocean up to about 60 kilometers off the coast around the clock.
Japanese Agency to Monitor Conditions Under Seabed
In preparation for a massive earthquake in the Nankai Trough, the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and other organizations have launched a project to monitor subtle bedrock movements and distortion with devices installed below the seabed off the Kii Peninsula. Researchers hope the constant monitoring devices will help predict a giant earthquake. They will be installed about 980 meters below the seabed, the lowest level in the world for such equipment.
The Yomiuri Shimbun reported: “JAMSTEC and the Meteorological Agency are currently monitoring seismic activity with 20 seismometers installed on the seabed in the Sea of Kumano, southeast of the Kii Peninsula. A massive earthquake is predicted to occur at some point in the Sea of Kumano. JAMSTEC and the agency's current monitoring of the area is akin to applying a stethoscope to the seabed. However, the seabed-based devices only enable them to monitor seismic waves that have reached the seabed and therefore do not directly monitor activities inside the crust. [Source: Yomiuri Shimbun, January 6, 2013]
Under the envisaged project, JAMSTEC aims to monitor crustal movements more accurately by inserting monitoring devices similar to endoscopes deep into the crust below the seabed. In 2010, JAMSTEC and other organizations used the deep-sea drilling vessel Chikyu to burrow about 980 meters below the seabed, which is itself about 1,900 meters deep, at a location 80 kilometers off Shingu, Wakayama Prefecture.
There is a boundary between plates about 7,000 meters below the seabed and a spray fault 3,000 meters above the boundary. This zone is called a seismogenic zone, where large earthquakes have occurred in the past. A steel pipe was inserted into the hole with a strain gauge to check distortion in the bedrock, along with a seismometer, a thermometer and a water pressure gauge installed inside the pipe. The strain gauge can detect when the volume of the bedrock expands or contracts by as little as one billionth of its original size. All relevant data will be transmitted to a base station on land via a cable and relayed to the Meteorological Agency and other bodies. Activities inside the crust below the seabed will be monitored around the clock.
Computer simulations have indicated that there may be certain changes if a massive earthquake is imminent, such as shifts in the locations of points where subtle earthquake motions are active or a slowing down in subduction of the crust. The envisaged project is expected to detect these phenomena in advance with devices installed inside the crust.
Seafloor Seismic Alert System
In July 2013, Jiji Press reported: The Japanese “government started work to install undersea seismometers and tsunami observation equipment in wide areas off the Pacific coast, including along the Japan Trench, in a government-sponsored project designed to enable quicker and more accurate quake and tsunami alerts. The observation system will be placed in offshore areas from the Tokachi region of Hokkaido down to the Boso Peninsula in Chiba. [Source: Jiji Press, July 10, 2013 |=|]
“The 32 billion yen project of the Education, Culture, Sports, Science and Technology Ministry comes over two years after the magnitude-9.0 Great East Japan Earthquake of March 11, 2011. Centered near the Japan Trench off Miyagi Prefecture, the quake generated massive tsunami. The installation work will be carried out in stages at six target areas, including one along the Japan Trench, for completion by the end of March 2015. |=|
“The equipment will be first installed in the area off the Boso Peninsula because it is at risk of a powerful earthquake and is close to the Tokyo metropolitan area. The cylinder-shaped seismometers and tsunami observation devices will be joined by a total of 5,700 kilometers of cables. The system, which will have 150 observation points, detects tsunami through changes in ocean water pressure. |=|
Agency to Revamp Tsunami Warnings
Drawing on lessons from incorrect tsunami warnings issued after the Great East Japan Earthquake, the Meteorological Agency has decided to change tsunami warnings from announcing estimated tsunami heights after large earthquakes to simpler warnings such as, "A huge tsunami is coming." When an earthquake is estimated to have a magnitude of more than 8, the agency will use wording such as "huge" or "high," urging people in coastal areas to flee immediately to high ground in its initial warnings, officials said. [Source: Yomiuri Shimbun, February 1, 2011]
At the time of the March 11 earthquake and tsunami, the agency issued warnings three minutes later, estimating the magnitude as 7.9. It also said the tsunami heights would be "six meters in Miyagi Prefecture" and "three meters in Iwate and Fukushima prefectures."It was later learned the actual magnitude of the earthquake was 9, with the ensuing tsunami 10 meters or higher.
Given the current level of technology, it is extremely difficult to accurately determine the size of earthquakes with magnitudes greater than 8 within three minutes, the agency officials said. Because of this, when an earthquake estimated to have a magnitude in excess of 8 occurs, the agency will not specify estimated tsunami height in initial warnings."Major" and "large" tsunami warnings that have so far been issued will be replaced with the words "huge" and "high," respectively, they said. In addition, phrases such as "tsunami similar to those after the Great East Japan Earthquake are expected" will be used to help people understand the scale of tsunami in comparison with past tsunami.
In initial warnings the agency will call on people in coastal regions to immediately move to elevated places, they said. In second-stage warnings to be issued about 15 minutes after an earthquake, its magnitude and tsunami height estimates will be issued. The tsunami height forecasts, however, will be simplified to five categories: one meter, three meters, five meters, 10 meters and more than 10 meters, to take the place of the current eight levels of classification, according to the officials.
Creating and Emergency Tsunami Warning System
The Japan Meteorological Agency wrongly estimated the Great East Japan Earthquake had a magnitude of 7.9, considerably lower than its actual size of 9. This meant it predicted a tsunami with a maximum height of six meters in Miyagi Prefecture and three meters in Fukushima and Iwate prefectures. This forecast was much lower than the actual height of the tsunami and was a major cause of the delay in evacuating these areas. This miscalculation occurred because the formula used by the agency to measure quakes cannot accurately measure an earthquake with a magnitude of 8 or stronger. [Source: Yomiuri Shimbun, February 3, 2012]
To reduce the impact of natural disasters on the Japanese archipelago, it is imperative to expand the nation's space and underwater surveillance networks. To rectify this situation, the government has begun a project to create an "emergency tsunami warning system" that will be able to make direct tsunami observations and will be able to forecast the height of waves when they hit the coast. This would be the tsunami equivalent of the earthquake warning system that makes rapid forecasts on earthquake intensities throughout the nation, based on their initial tremors.
In developing the system, the government is planning to lay cable-connected seismographs and tsunami gauges from fiscal 2012. They will be placed on the sea floor at 150 locations off Nemuro, eastern Hokkaido, to areas off the Boso Peninsula, Chiba Prefecture. Along the Nankai Trough, a deep trench in the Pacific Ocean of Shikoku where a magnitude-9 earthquake is predicted, the number of observation devices will be increased from seven to 15 by the Japan Coast Guard. When the project is completed, it will be possible to make detailed measurements of the amount of seismic energy accumulated on the borders of tectonic plates that have collided in the trough.
Japan's 1,000-Year-Old Tsunami Warning
José Holguín-Veras, an engineering professor at Rensselaer Polytechnic Institute in New York, wrote in the Los Angeles Times: After the March 2011 earthquake and tsunami “in a refugee center on the beautiful island of Miyatojima, at the entrance to Matsushima Bay, I stumbled on a story that, by its reach back in time, taught me something unexpected: Collective memory, as much as science and engineering, may save your life. After a long day of field work, my colleagues and I were chatting with a community leader, Koutaro Ogata, from a fishing village called Murohama. We asked what had happened to him in the moments after the earthquake. He told us that he and his neighbors were well aware that a large earthquake would generate a large tsunami and they knew, particularly, what to do because "a thousand years ago" a massive earthquake and tsunami had all but wiped out Murohama. [Source: José Holguín-Veras, Los Angeles Times, March 11, 2012]
This is the story he told. A millennium ago, the residents of Murohama, knowing they were going to be inundated, had sought safety on the village's closest hill. But they had entered into a deadly trap. A second wave, which had reached the interior of the island through an inlet, was speeding over the rice paddies from the opposite direction. The waves collided at the hill and killed those who had taken refuge there. To signify their grief and to advise future generations, the survivors erected a shrine.
This story might not have captured my attention if it hadn't been for a fortuitous coincidence. The day before, an engineering colleague, Eiichi Taniguchi, had told me that researchers at Tohoku University in Sendai, Japan, had found sediments indicating that a huge tsunami had hit Miyatojima about 1,000 years ago. Intrigued by the possibility of a connection between oral history and geological evidence, I asked the community leader if "a thousand years ago" was a figure of speech or an estimate of time.
To my astonishment, he indicated that it was in no way a figure of speech. Village elders had reviewed the local temple's records and found reports pinpointing a large tsunami 1,142 years ago. It was most likely the result of the massive Jogan Jishin earthquake of 869, which devastated the Sanriku coast. Thirty years before the great Mayan cities were abandoned, at the height of the Muslim and Chinese empires, when Europe was in the midst of the Early Middle Ages (and 600 years before Columbus stumbled into the Americas), a community of unknown fishermen honored their dead and successfully sent a warning to future generations.
Some 50 generations later, on March 11, 2011, the Murohama tsunami warning tower — which was supposed to sound an alarm — was silent, toppled by the temblor. Still, without the benefit of an official warning system supported by modern science, the locals relied on the lesson that had been transmitted generation to generation for 1,000 years. "We all know the story about the two tsunami waves that collided at the shrine," I was told.
Instead of taking refuge on the closest hill, the one with the shrine, they took the time to get to high ground farther away. From the safety of their vantage point they saw two tsunami waves colliding at the hill with the shrine, as they did long ago. Tragically, not everyone made the right choice; I was told of at least one person who died. Later, I saw the shrine — a simple clearing by the side of a hillside road, with stone tablets and roughly made figures — and I heard the old story and the new one again: A community remembered what it had been told and did the right thing.
I have to admit that I have not been able to keep this story of survival out of my mind. I know that science and engineering save lives. But in this instance neither did much to help. A message sent into the future 1,000 years ago did. Reaching out from the distant past, long-gone ancestors — and a deeply embedded story — saved their children.
Warnings from the Tsunami Stones
After the 2011 tsunami, Evan Osnos wrote in The New Yorker: Up and down the battered coast, [residents] rediscovered gnarled stone tablets, some of them hundreds of years old, which had been left by ancient ancestors at precise points on the shore to indicate the high-water marks of previous tsunamis. The inscriptions implored future generations never to build closer to the water again. “No matter how many years may pass,” read one, “do not forget this warning.”
Reporting from Aneyoshi in northeast Honshu, Martin Fackler wrote in the New York Times, “The stone tablet has stood on this forested hillside since before they were born, but the villagers have faithfully obeyed the stark warning carved on its weathered face: “Do not build your homes below this point!? Residents say this injunction from their ancestors kept their tiny village of 11 households safely out of reach of the deadly tsunami that struck Japan in March 2011. “The waves stopped just 300 feet below the stone.” “They knew the horrors of tsunamis, so they erected that stone to warn us,” said Tamishige Kimura, 64, the village leader of Aneyoshi. In April a university group said the waves reached their greatest height in Aneyoshi: 127.6 feet, surpassing Japan’s previous record of 125.3 feet reached elsewhere in Iwate Prefecture by the 1896 tsunami.” [Source: Martin Fackler, New York Times, April 20, 2011]
“Hundreds of so-called tsunami stones, some more than six centuries old, dot the coast of Japan, silent testimony to the past destruction that these lethal waves have frequented upon this earthquake-prone nation. But modern Japan, confident that advanced technology and higher seawalls would protect vulnerable areas, came to forget or ignore these ancient warnings, dooming it to repeat bitter experiences when the recent tsunami struck.”
“The tsunami stones are warnings across generations, telling descendants to avoid the same suffering of their ancestors,” Itoko Kitahara, a specialist in the history of natural disasters at Ritsumeikan University in Kyoto told the New York Times. “Some places heeded these lessons of the past, but many didn’t.”
The flat stones, some as tall as 10 feet, are a common sight along Japan’s northeastern shore, While some are so old that the characters are worn away, most were erected about a century ago after two deadly tsunamis here, including one in 1896 that killed 22,000 people. Many carry simple warnings to drop everything and seek higher ground after a strong earthquake. Others provide grim reminders of the waves’ destructive force by listing past death tolls or marking mass graves.
Some stones were swept away by the March 2011 tsunami. Fackler wrote: “Aneyoshi’s tsunami stone is the only one that specifically tells where to build houses. But many of the region’s names also seem to indicate places safely out of the waves’ reach, like Nokoriya, or Valley of Survivors, and Namiwake, or Wave’s Edge, a spot three miles from the ocean that scholars say marks the farthest reach of a tsunami in 1611.”
“In Aneyoshi, the tsunami stone states that “high dwellings ensure the peace and happiness of our descendants.” Mr. Kimura called the inscriptions “a rule from our ancestors, which no one in Aneyoshi dares break.” The four-foot-high stone stands beside the only road of the small village, which lies in a narrow, cedar-filled valley leading to the ocean. Downhill from the stone, a blue line has been newly painted on the road, marking the edge of the tsunami’s advance. Just below the painted line, the valley quickly turns into a scene of total destruction, with its walls shorn of trees and soil, leaving only naked rock. Nothing is left of the village’s small fishing harbor except the huge blocks of its shattered wave walls, which lie strewn across the small bay.”
Disregarding the Warnings of the Tsunami Stones
Fumihiko Imamura, a professor in disaster planning at Tohoku University in Sendai told AP, Earlier generations also left warnings in place names, calling one town “Octopus Grounds” for the sea life washed up by tsunamis and naming temples after the powerful waves. “It takes about three generations for people to forget. Those that experience the disaster themselves pass it to their children and their grandchildren, but then the memory fades,” he said.
Martin Fackler wrote in the New York Times, “Local scholars said only a handful of villages like Aneyoshi heeded these old warnings by keeping their houses safely on high ground. More commonly, the stones and other warnings were disregarded as coastal towns grew in the boom years after World War II. Even communities that had moved to high ground eventually relocated to the seaside to be nearer their boats and nets.” [Source: Martin Fackler, New York Times, April 20, 2011]
“As time passes, people inevitably forget, until another tsunami comes that kills 10,000 more people,” said Fumio Yamashita, an amateur historian in Iwate Prefecture, where Aneyoshi is situated. He has written 10 books about tsunamis. Mr. Yamashita, 87, who survived the recent tsunami by clinging to a curtain after waters flooded the hospital where he was bedridden, told the New York Times that Japan had neglected to teach its tsunami lore in schools. He said the nation had put too much store instead in new tsunami walls and other modern concrete barriers, which the waves easily overwhelmed last month.
Mr. Kimura, a fisherman who lost his boat in the 2011 tsunami, told the New York Times the village first moved its dwellings uphill after the 1896 tsunami, which left only two survivors. Aneyoshi was repopulated and moved back to the shore a few years later, only to be devastated again by a tsunami in 1933 that left four survivors. After that, the village was moved uphill for good, and the stone was placed. Mr. Kimura said none of the 34 residents in the village today know who set up the stone, which they credit with saving the village once before, from a tsunami in 1960. “That tsunami stone was a way to warn descendants for the next 100 years that another tsunami will definitely come,” he said.
The village’s mostly older residents said they regretted not making more of an effort to teach younger residents such tsunami-survival basics as always to seek higher ground. “We are proud of following our ancestors,” the children’s grandfather, Isamu Aneishi, 69, said, “but our tsunami stone can’t save us from everything.”
“For most Japanese today, the stones appear relics of a bygone era, whose language can often seem impenetrably archaic, Fackler wrote. “However, some experts say the stones have inspired them to create new monuments that can serve as tsunami warnings, but are more suited to a visual era of Internet and television. One idea, put forth by a group of researchers, calls for preserving some of the buildings ruined by the recent tsunami to serve as permanent reminders of the waves’ destructive power, much as the skeletal Atomic Bomb Dome in Hiroshima warns against nuclear war.” “We need a modern version of the tsunami stones,” said Masayuki Oishi, a geologist at the Iwate Prefectural Museum in Morioka.
Only 50 Percent of Schools Were Ready for the 2011 Tsunami
Only 50.3 percent of schools in Iwate, Miyagi and Fukushima prefectures affected by the March 2011 tsunami had evacuation plans in their crisis management manuals, according to an education ministry survey and an article in the Yomiuri Shimbun. The survey also found that many students died in the tsunami because they were sent home just after the earthquake struck. [Source: Yomiuri Shimbun, May 31, 2012]
“Of the 149 schools hit or expected to be hit by tsunami, only 75 had evacuation plans in place, according to the survey. Among the 149 schools, 131 were inundated by tsunami. Sixty-nine schools that were inundated were not designated as at risk of tsunami on hazard maps, according to the survey. Among 71 schools in the at-risk areas, 53 were flooded, but 27 did not conduct tsunami drills, the survey said.
“Among primary schools that had conducted evacuation drills, 11.4 percent said students panicked due to fear and anxiety on March 11, 2011, the survey said. Among primary schools that had not conducted such drills, 28.6 percent said students panicked. Students were present at 2,052 schools when the earthquake hit. Asked how they responded to the earthquake, 79.3 percent of the schools said they handed over the students to their parents to be taken home. Only 21.7 percent said they had difficulty with the idea of sending the students home and kept them at school instead. Asked about students who died in the tsunami, in 22 of the 64 cases students were said to have been on their way home. There were 16 cases in which students died after they arrived home from school.
“After the disaster, some schools changed disaster management policies. The municipal government of Iwanuma, Miyagi Prefecture, has started deciding on evacuation sites based on the locations of students' homes and routes they take to and from school.
Image Sources: Disaster Prevention Research Institute, University of Kyoto, USGS
Text Sources: New York Times, Washington Post, Los Angeles Times, Daily Yomiuri, Times of London, Japan National Tourist Organization (JNTO), National Geographic, The New Yorker, Time, Newsweek, Reuters, AP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.
Last updated January 2014