2011 Tōhoku earthquake and tsunami

• 1. Seismic Mechanics And Magnitude

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  On the 11th of March 2011, at 14:46:24 JST, a massive undersea earthquake struck the Pacific Ocean east of Japan's Oshika Peninsula. The tremor lasted approximately six minutes and registered a magnitude between 9.0 and 9.1 on the moment magnitude scale. This event became the most powerful earthquake ever recorded in Japanese history and the fourth strongest globally since modern seismography began in 1900. Initial reports from the United States Geological Survey estimated the quake at 7.9 Mw before quickly upgrading it to 8.8, then 8.9, and finally 9.0. On the 11th of July 2016, officials further revised the measurement to 9.1 Mw. The hypocentral region extended from offshore Iwate Prefecture to offshore Ibaraki Prefecture. Analysis showed the rupture covered a length of roughly 500 kilometers and a width of about 200 kilometers. The main shock was preceded by large foreshocks, including a 7.2 Mw event on the 9th of March. Hundreds of aftershocks followed, with over 800 registering 4.5 Mw or greater. Aftershocks continued for years, including one measuring 7.1 Mw on the 26th of October 2013. The earthquake shifted Honshu eastward and moved the Earth's axis by an estimated 10 centimeters. This shift increased Earth's rotational speed by 1.8 microseconds per day. Ground motion reached a maximum intensity of Shindo 7 in Kurihara, Miyagi Prefecture. Seismic stations recorded peak ground acceleration values as high as 2.99 g. Soil liquefaction caused significant damage in reclaimed land areas around Tokyo, particularly in Urayasu and Chiba City.

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• 2. Tsunami Propagation And Impact

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  The tsunami generated by the earthquake inundated approximately 560 square kilometers of Japan's coastline. Waves reached heights of up to 40.5 meters at the Aneyoshi fishery port near Miyako in Iwate Prefecture. Residents of Sendai had only eight to ten minutes of warning before the water arrived. More than a hundred designated evacuation sites were washed away by the surge. Snowfall accompanied the tsunami, hindering rescue efforts significantly. In Ishinomaki, the city with the most deaths, temperatures dropped to minus 1 degree Celsius when the wave hit. At Tarō, Iwate, the tsunami climbed up a mountain slope reaching 185 meters above sea level. The wave traveled throughout the Pacific Ocean, striking North and South America from Alaska to Chile. Chile's coast experienced waves up to 3 meters high despite being thousands of kilometers away. In California, waves damaged docks and harbors causing over US$10 million in losses. Surges hit Vancouver Island prompting evacuations and banning boats for 12 hours. The Philippines saw waves up to 2 meters high on its eastern seaboard. Authorities evacuated patients from Boram Hospital in Wewak, Papua New Guinea after waves caused an estimated US$4 million in damage. Hawaii reported infrastructure damage totaling US$3 million. A wave completely submerged Midway Atoll's reef inlets killing more than 110,000 nesting seabirds. The tsunami broke icebergs off the Sulzberger Ice Shelf in Antarctica. Debris from the event spread globally, including a soccer ball found in Alaska and a Japanese motorcycle discovered in British Columbia.

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• 3. Fukushima Nuclear Meltdowns

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  Tsunami waves overtopped seawalls at the Fukushima Daiichi Nuclear Power Plant destroying diesel backup power systems. Three reactors suffered meltdowns leading to severe cooling failures. Heat build-up generated hydrogen gas which accumulated within the upper refueling hall without ventilation. Gas explosions forcefully ejected blast panels from the structure. Radiation levels inside the plant reached up to 1,000 times normal levels while outside levels rose eight times higher. Over 200,000 people were evacuated from areas surrounding the facility. Residents within a radius of 20 kilometers of the plant and 10 kilometers of the Daini plant were ordered to leave. Radioactive water discharged into the ocean from Units 1, 2, and 3. Radioactive iodine was detected in tap water across multiple prefectures including Tokyo and Chiba. An aftershock on the 7th of April caused loss of external power to the Rokkasho Reprocessing Plant. Onagawa Nuclear Power Plant lost three of its four external power lines temporarily losing cooling function for spent fuel pools. A spill of radioactive water occurred at Onagawa following that aftershock. Experts described the disaster as more complicated than Chernobyl but less severe in terms of immediate fatalities. The discharge of radioactive water continued to be confirmed in later analysis.

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• 4. Human Casualties And Demographics

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  Official figures released in 2021 reported 15,894 deaths directly caused by the earthquake and tsunami. Another 2,526 people remain missing as of recent counts. In Miyagi Prefecture alone, 10,567 people died while Iwate recorded 5,145 deaths. Fukushima accounted for 3,920 fatalities with smaller numbers in other regions like Ibaraki and Chiba. Drowning accounted for 90.64% or 14,308 bodies recovered. Burning caused 0.9% or 145 deaths while others were crushed by heavy objects. Elderly individuals over age 60 comprised 65.8% of all deaths. As many as 100,000 children were uprooted from their homes during the school day. Three hundred seventy-eight elementary, middle-school, and high school students were killed leaving 158 others missing. Okawa Elementary School in Ishinomaki lost 74 of its 108 students and 10 of 13 teachers due to evacuation decisions. Twenty-three six children became orphaned across Iwate, Miyagi, and Fukushima prefectures. One thousand five hundred eighty children lost either one or both parents. Nineteen foreign nationals confirmed dead included two English teachers from the United States and a Canadian missionary. Governments buried thousands of bodies in hastily dug mass graves because crematorium capacity was exceeded. Shortages of kerosene and dry ice hampered preservation efforts. By March 2012, the government recognized 1,331 deaths indirectly related to harsh living conditions after the disaster.

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• 5. Infrastructure Destruction And Recovery

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  The National Police Agency reported 45,700 buildings destroyed and 144,300 damaged by the quake and tsunami. Damage included 29,500 structures in Miyagi Prefecture and 12,500 in Iwate Prefecture. Three hundred hospitals with at least 20 beds suffered damage with 11 completely destroyed. An estimated 24 to 25 million cubic meters of rubble and debris filled Japanese landscapes. Fifteen ports located in the disaster zone were destroyed or severely damaged including Hachinohe, Sendai, Ishinomaki, and Onahama. The Port of Chiba served the hydrocarbon industry but faced severe disruption. All fifteen ports reopened to limited ship traffic by the 29th of March 2011. A total of 319 fishing ports representing about 10% of Japan's fleet sustained damage. Most restored operations by the 18th of April 2012. The Fujinuma irrigation dam in Sukagawa ruptured washing away five homes and killing four people. At least 1.5 million households lost access to water supplies immediately after the event. By the 21st of March 2011 this number fell to 1.04 million. Around 4.4 million households were left without electricity while 1.5 million lacked water. Approximately 230,000 automobiles and trucks were damaged or destroyed. Residents requested deregistration for 15,000 vehicles as unrepairable by end May 2011. Fires broke out at Cosmo Oil refinery in Ichihara injuring six people and destroying storage tanks over ten days. Another fire occurred at a JX Nippon Oil & Energy refinery in Sendai hindering extinguishing efforts due to tsunami warnings.

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• 6. Economic Consequences And Energy Crisis

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  Early estimates placed insured losses from the earthquake alone between US$14.5 billion and $34.6 billion. Total estimated economic damage exceeded $300 billion making it the costliest natural disaster in history. A 2020 study found the disaster resulted in a 0.47 percentage point decline in Japan's real GDP growth during the following year. The Bank of Japan offered ¥15 trillion (US$183 billion) to banking systems on the 14th of March 2011 to normalize market conditions. Rolling blackouts began on the 14th of March affecting Tokyo Kanagawa Eastern Shizuoka Yamanashi Chiba Ibaraki Saitama Tochigi and Gunma prefectures. Tōhoku Electric Power left 4.4 million households without electricity while TEPCO capacity dropped by 21 GW. Steel manufacturers contributed power with Sumitomo Metal Industries producing up to 500 MW and JFE Steel providing 400 MW. Auto makers agreed to operate factories on weekends to conserve energy during summer months. Peak consumption recorded by TEPCO reached 49.22 GW which was 10.77 GW lower than the previous year. Overall electricity consumption dropped 14% less than the prior year. The government asked the public to conserve electricity until 2016 when supply met demand. Three steel companies provided electricity produced by their own conventional stations for distribution. Voluntary reductions helped reduce predicted frequency and duration of blackouts. A legacy from the 1880s left Japan without a unified national power grid causing disparities between 50 hertz and 60 hertz systems.

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