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The Great East Japan Earthquake
Hideo Takagi
Preserving the Remains in Areas Struck by the Tsunami
-Applying the Aftermath of the Tragedy to Disaster Education and Enlightenment
Hideo Takagi
Professor of the Department of Earth Sciences, Faculty of Education and Integrated Arts and Sciences, Waseda University
The Greatest Tsunami in Hundreds of Years
The 2011 off the Pacific coast of Tohoku Earthquake recorded a moment magnitude (Mw) 9.0—fourth largest in recorded history—caused a major tsunami caused disaster that strikes only once every few hundred years. According to the information provided by various research institutes, a reverse fault with a very loose slope crumbled severely at the top surface of the subducting Pacific plate about twenty-four kilometers depth, and this is what is thought to have caused a vertical motion of the ocean floor across a very broad range.
Nearly twenty thousand people lost their lives in the Sanriku region in a huge tsunami during the 1896 Meiji-Sanriku Earthquake. The tsunami that struck is known to have reached a maximum of 38.2 meters above sea level. Furthermore, at least three thousand people lost their lives in the 1933 (Showa) Sanriku Earthquake. In addition, the tsunami from the Valdivia Earthquake (Mw9.5), which was the most powerful earthquake ever recorded, raced across the Pacific Ocean for a day and killed a hundred and forty-two people on the Sanriku coast and throughout Japan in 1960. Other major tsunamis have also been recorded on the Sanriku coast in 1611, 1677, 1793, 1835, and 1856. This means that the region is struck by tsunamis every few decades. When looking further back in history, the Sendai Plain was entirely engulfed during the Jogan Earthquake of July 13th, 869, and it has been pointed out that the tsunami back then resembles in nature the tsunami of March 11th this year. It has been geologically proven that major tsunamis also strike Sendai Plain every several hundreds to one thousand years.
Because of its geomorphic characteristics of being on a deeply indented (rias) coastline, the Sanriku region was equipped with preparations such as coastal levees in Kesennuma which were considered the world’s foremost tsunami breakwater. However, they were destroyed by the last tsunami. Although the people in the coastal areas there had the highest awareness of tsunamis in the nation, many of them could not run in time from the tsunami that far exceeded their expectations, reaching more than ten meters in height, claiming the lives of many victims, and leaving nothing but piles of rubble.
The Region Protected by the Monument of its Predecessors
Photo 1: The grand tsunami monument in Aneyoshi, Miyako City built after the Showa-Sanriku Earthquake. Provided by Dr. Masayuki Oishi
The message, “A house on a high land brings peace and happiness to your children and grandchildren - Remember the ravages of the great tsunami - Do not build any houses below this point” is engraved on the great tsunami disaster monument that stands in the Aneyoshi area of Miyako City (Photo 1). According to a survey conducted by the Tokyo University of Marine Science and Technology, this huge tsunami reached 38.9 meters above sea level in height, exceeding the height of the tsunami that struck during the Meiji-Sanriku Earthquake, which had been the highest ever recorded in Japan. According to the report by curator Masayuki Oishi of the Iwate Prefectural Museum, this stone monument was built about sixty meters above sea level, and the tsunami reached a distance of about ninety meters short of the stone monument. No houses were built below this monument, so the Aneyoshi area was not afflicted by the tsunami.
The Sanriku coast had been seeking recognition from Geopark (parks supported by UNESCO that promote the connection between people and the earth) for a year. Geoparks are parks that not only conserve geologic and topographic assets, but also enjoy the connection between the ecology and people’s cultures, history, and traditions, as well as the stimulating of education and sightseeing in their regions. Currently, there are fourteen locations (including four in the Global Geoparks Network) in Japan that are officially recognized. Disaster education is also an important theme in Geoparks, and an important theme in this particular region was the battle against recurring tsunami disasters.
The Significance of Revealing Conditions as They Truly Are
The image of the huge sightseeing ship that ended up on top of an inn in Otsuchi town (Photo 2) when the tsunami struck was widely shown, astonishing people all over the world. Ships like these can actually be important remains of the disaster. It has been reported, however, that this one is scheduled to be dismantled. It may just be symbolic of the nightmare that the people in the area affected by the tsunami want to forget.
The tsunami disaster is likely to gradually fade from the memories of the townspeople when the town is restored and several decades have passed. We are now entering an age where university students do not know about the Great Hanshin-Awaji Earthquake. Many visitors including students on their school excursions go to see the remains of natural disasters such as those at the Nojima Fault Preservation Museum, which preserves the active faults that appeared on the surface of the ground during the Southern Hyogo Earthquake in 1995, along with the Mount Usu Eruption Memorial Park to which I annually lead the students of the Department of Earth Sciences, which I belong to (Photo 3) and the site of the elementary school building that disappeared with the pyroclastic flows from Mount Unzen. The latter two locations are also included as the members of the Global Geoparks Network, and the remains of the volcanic disasters are internationally recognized as important geosites as well. Preserving the sites of disasters such as earthquakes and volcanic eruptions and showing how they truly are greatly contributes to education and raising awareness on disaster prevention, the revitalization of the local areas, and so on. Materials such as written documents, photos, and images alone do not provide enough of a sense of reality because it is meaningful only when it actually exists at the local sites.
Photo 2: The sightseeing ship Hamayuri of Kamaishi on top of the Otsuchi Town inn
Photo 3: The remains of the Usu Volcano eruption in 2000 (foot of Mt. Nishiyama)
Raising Awareness and Education on Tsunami Disaster Prevention for the World
The most devastating tsunami in history, which killed over two hundred and twenty thousand people during the Indian Ocean Earthquake (Mw9.1) on December 26th, 2004, is still fresh in our minds. Several ships that washed up on the shores of Aceh City in Indonesia, where the damage from the tsunami was extensive, are still preserved. Just three months after the Indian Ocean Earthquake, which was the second largest earthquake in recorded history, an Mw8.6 earthquake struck off the coast of Sumatra and another one of Mw8.5 struck three years later. This shows that it is dangerous to assume that once such a major earthquake and tsunami strike, there will not be any more for a long time.
Restoration plans that focus on tsunami disaster prevention are expected to be formulated immediately and it would be desirable for them to include the preservation of the remains of the tsunami-afflicted areas in a way that provides a sense of reality with a long-term view. They should also be applied to raising awareness and education on tsunami disaster prevention throughout the world and for those on the Pacific coast of western Japan, where the probability rate of getting hit by the Nankai, Tonankai, and Tokai earthquakes during the first half of this century is high. As a supporter of Geoparks, I present this proposal as those who have been affected are leading very restricted lives, there are still many people who are missing, and because I feel that it is only a matter of time before the rubble is removed or collapses.
Hideo Takagi
Professor of the Department of Earth Sciences, Faculty of Education and Integrated Arts and Sciences, Waseda University
[Profile]
Assumed the position of Professor in 1996 after serving as Research Associate of the School of Education, Waseda University in 1982 and as Assistant Professor. Specially selected Geopark board member and Geopark Assisting Committee member of the Geological Society of Japan, and member of the Japan Geopark Committee. Holds a Doctor of Science degree from Nagoya University.
[Major Publications]
Basic Earth Science (partner author, Asakura Publishing Co., Ltd.), Earth, Environment, and Resources (editor and partner author, Kyoritsu Shuppan Co., Ltd., 2009) Field Geology 7 “Metamorphism and Deformation”(editor and partner author, Kyoritsu Shuppan Co., Ltd., 2009)
Takagi Lab Webpage
*The commentary On the off the Pacific coast of Tohoku Earthquake (Great East Japan Earthquake and Disaster) ver. 3 was posted on the news column of the Department of Earth Sciences, School of Education webpage
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