On March 11, 2011, the magnitude 9.0 Great Tōhoku Earthquake struck Honshu, the main island of Japan at 2:46 pm local time. The epicenter was 30 km deep, located off of the coast. It was the largest earthquake ever to hit Japan and the fourth largest earthquake on record. a rupture occurred at the convergent fault boundary in the Japan Trench and a 300 km long by 150 km wide section of the subduction zone slipped as much as 50 meters, the largest fault slip ever recorded. The Tōhoku region in northeast Honshu experienced violent shaking for six minutes and was shifted east by 2.4 meters. Scientists believe that clay helped lubricate the fault to create such extreme movement because it holds water and becomes slick, removing friction from the plate collision. There is a deep layer of clay on the Pacific plate and as it subducts beneath the North American plate a thin layer is scraped off, leaving an accretionary wedge of clay coating the boundary. Low-frequency infrasound waves generated by the earthquake were even detected 255 km above the earth in space by a satellite.
A colossal tsunami followed the quake caused by a combination of upward thrusting of the seafloor from the earthquake and a submarine mass movement event. Remnants of a 40 km by 20 km rotational slump were observed on the slope of the Japan Trench. Waves as high as 38 meters moved as fast as a jet plane, 700 km/hr and flooded the island up to 10 km inland. The tsunami had record run-up recordings at 38.8 meters above sea level. Abnormally large waved were documented all across the Pacific from the west coast of North America and South America to Russia. Also satellite imagery showed that the waves contributed to Antarctic glacier calving. [youtube]https://www.youtube.com/watch?v=w3AdFjklR50[/youtube] [youtube]https://www.youtube.com/watch?v=j0YOXVlPUu4[/youtube]
Japan is no stranger to earthquakes and tsunamis because it is located near multiple late boundaries on the Pacific Ring of Fire. The nation experiences one fifth of the world’s powerful quakes and the word tsunami itself is Japanese. Japan is extremely prepared for these hazards and has heavily invested in preparedness and mitigation plans. Over 1000 seismographs and hundreds of tide sensors are scattered around the islands comprising the world’s most advanced early-warning system. Alerts are sent out automatically over every medium of communication including personal cell phones and loudspeaker systems. Japan has built many hard structures along the coasts such as tsunami walls, flood gates and breakwaters. Building codes are strict and constantly updated with continuous research and assessment on building safety and design. Tall buildings are designed to sway and are set on deep foundations, many supported with shock absorbers. Concrete structures are built with a steel frame to give them ductility to be more resilient to a lateral load. Disaster shelters are prepared in case of emergency and some public spaces in cities are constructed with a secondary purpose as refuge zones. These spaces are cleverly designed as permanent installations ready to house and sustain people at a moment’s notice with underground food and water reserves and innovations such as solar-powered charging stations and benches that turn into stoves for cooking. Disaster preparedness is deeply ingrained into society and has become part of Japanese culture. People constantly practice intensive drills and receive briefings on potential hazards from the time they begin school.
Japan is one of, if not the most prepared nation in the world for these types of hazards. The population is also not considered vulnerable in a country with the third largest GDP in the world that is known for its technological innovation and advancements. Japan can handle earthquakes that would cause considerable damage elsewhere and regularly experiences quakes with a magnitude between 4.0 – 5.0. However, the 2011 “trifecta of tragedy”, earthquake, tsunami and resulting nuclear accident was the perfect storm. Like the swiss cheese activity in class, everything lined up perfectly to make this one of the worst disasters in history. The death toll as of April 2015 is 15,890, another 2,590 people were reported as missing and presumed dead and 6,152 injuries were recorded. An overwhelming majority of the deaths and injuries were due to the tsunami. Hundreds of thousands of buildings were damaged or destroyed, over 25 million tons of debris was generated in the 3 worst affected prefectures and hundreds of fires were started from broken electric and gas lines. The damage has cost Japan $300 billion, making it the most expensive natural disaster in history. Considerable economic losses were suffered by other countries around the pacific as well. Response efforts were divided among all departments of the Japanese government who were immediately mobilized and dispatched. Despite their organization, no amount of preparation and prior planning could have anticipated the 2011 catastrophe. Transporting supplies was impeded by the damage to roads and infrastructure and contributed to the physical and psychological distress of refugees. Flooded areas did not drain naturally due to subsidence of the land from the quake. Floodwall failure and standing water further hindered supply distribution and posed an obstacle for search and rescue. Certain areas were only accessible by helicopter for 2 weeks. The combined loss of power from the Fukushima coast, one of Japan’s largest single electric source regions and the shut off of the island’s other reactors caused additional setbacks to emergency response efforts.
A “state of nuclear emergency” was declared because the tsunami also caused the world’s first triple nuclear meltdown at the Fukushima Daiichi Nuclear Power Plant. The International Atomic Energy Agency gave the Fukushima Daiichi nuclear disaster a 7 rating on the International Nuclear and Radiological Event Scale, the highest rating and the same as the 1986 Chernobyl nuclear disaster. 140,000 people who lived within 20 km of the Fukushima reactors were evacuated and many are still displaced. Radiation continues to leak from the reactors and irradiated water is still being released into the ocean. TEPCO (Tokyo Electric Power Co.) has been unable to remove hundreds of dangerous fuel rods as the clean up process moves into its fourth year. Japan had relied on nuclear power for 30% of its electricity supply prior to the Fukushima accident but most of the 54 reactors in the country have not been reopened. The loss of this power source has contributed to a national energy crisis as Japan has little fossil fuel reserves and now depends on imports for 80-90% of its energy. The psychological effects of the disaster have had a large burden on Japanese society, with a spike in PTSD, depression and suicide rates among people living in the most impacted regions.
I chose this disaster because I find it incredibly fascinating and it has had such monumental consequences that are still being felt and dealt with today. The earthquake and tsunami struck when I was finishing up my senior year of high school so I remember how much it was covered by the news. I am also very interested in the Fukushima nuclear disaster and I have done a lot of research on it but not so much into the actual natural disaster that caused it.