I decided to choose the 2011 Tohoku earthquake and Tsunami, which devastated the northeastern coast of Japan. A prime reason for choosing this particular event was that I had heard about this event prior to this class, albeit I had never done any real research on the topic. Additionally, I was interested in learning what types of mitigations are used in a country that experiences earthquakes at a high frequency. I also have an interest in visiting Japan for travel and potentially for my career. Lastly, I chose this event because it was a domino effect in which it was the perfect example of anything that could happen, did happen. This does not mean that Japan’s mitigations we bad; it just means that they were not prepared for a disaster that would go down in history.
On March 11th, 2011, a 9.1 magnitude (Mw) earthquake occurred with its epicenter located 80 miles east of the city of Sendai and its hypocenter located 18.6 miles below the seafloor. The years of stress that were built up in this subduction zone also factored into the magnitude of the earthquake. Prior to the earthquake, there were multiple foreshocks, and following the earthquake, there were many aftershocks, several of which were above a 6.0 magnitude. This earth was one of the strongest earthquakes in history, yet it was not the primary cause of the damage that the northeastern coast of Japan would experience. It was mainly the tsunami that was generated from vertical movements from the Pacific plate subducting under the Okhotsk plate. The tsunami’s maximum runup height was close to 130 feet and inundated as far as 6 miles inland. The tsunami was quick, given it was local, and it arrived at the coast of Japan within 30 minutes. Again, the tsunami caused extensive damage as it swept away houses, cars, vegetation, and other debris. The earthquake and tsunami also caused many other hazards, such as landslides, liquefaction, wildfire, and the Fukushima nuclear disaster, which was on the same level as Chernobyl.
The death toll of this disaster was reported to be around 18,000 to 20,000 people but is not concrete due to missing persons. The elderly were the main demographic that was affected as more than half of the deaths were people aged 60 or older. It showed that beyond sea walls, there were not many other mitigations. Additionally, there was a heavy reliance on sea walls not failing, so when they did, that’s what made the event more disastrous. Some of the sea walls that had failed were as tall as 18 feet. The humanitarian response was immense as several countries, including, but not limited to, Canada, China, Australia, and the United States. Most countries sent resources to help with search & rescue, clearing debris, and reconstruction. This matter was resolved in months to a couple of years except for the area of Fukushima. The nuclear disaster that ensued at the Fukushima Daiichi plant was caused by the tsunami damaging the backup power supply, which caused the reactors to meltdown. Mass evacuation of the area occurred due to the radiation, and it took years for residents to be able to return; there are still dangerous areas to this day.
My conclusions revolved around how Japan did the best they did in light of how the severity of the event was on a historical level and could have been worse if they lacked the mitigations they had prior. The problem was the mitigations usually stopped at the sea walls, so after this incident, new building regulations were imposed and began reconstructing areas and adding other mitigations with the assumption that the sea wall would fail. Additionally, the sea walls were raised. Japan also needs to educate its population on tsunamis in the sense of comparing a given wave height to a common object like a house. This means their population needs to evacuate in the event of a tsunami as mitigations are more so geared at defending property, granted they do protect people. Lastly, an event comparable to this one was the Indian Ocean tsunami, which led to over 200,000 deaths due to the lack of mitigations, so it shows how much worse this could have been for Japan had they not had the mitigations they did.