Japan Braces for the Next “Big One” on the Anniversary of the Great East Japan Earthquake
The long-anticipated Nankai Trough earthquake and tsunami could cause 330,000 deaths and displace more than 8 million people.
What’s new: Monday, March 11, 2024 marked the 13th anniversary of the Great East Japan earthquake (東日本大震災), also known as the "Triple Disaster" or "3/11" in Japan. The name is derived from the magnitude 9.0 earthquake, the strongest ever recorded in Japan, the subsequent tsunami1 with waves up to 40 meters (130 feet) in some areas, and the near meltdown of the Fukushima Daiichi nuclear power plant after the tidal wave crashed ashore. This massive earthquake struck at 2:46 p.m. on March 11, 2011 and lasted more than 18 seconds, which seemed like an eternity at the time. Approximately 15,900 people2 have been confirmed dead as a result of the earthquake and devastating tsunami. More than 2,500 are still unaccounted for and presumed dead.
The anniversary has many in Japan thinking about the next "Big One," which already has a name. It is known as the Nankai Trough earthquake and tsunami. While no one knows when it will strike, the devastation caused by this killer megaquake will likely dwarf that of the Great East Japan earthquake.
Definitions: While Japan has been known for centuries as a nation prone to natural disasters, not much is known in the West about the coming Nankai Trough earthquake and tsunami.
What is the Nankai Trough? The Nankai Trough is a 4,000 meter (13,100 feet) deep trench-like landform that exists on the Pacific Ocean side from Shizuoka to Shikoku. This is where the Philippine Sea Plate, an oceanic plate, collides with and subducts into the Eurasian Plate, a land plate. Plate boundary earthquakes have occurred there regularly for thousands of years. The Philippine Sea Plate is moving northwest at a rate of 3 to 4 cm (1.2 ~ 1.6 inches) per year, accumulating 3 to 4 m (118 ~ 157 inches) of "strain," the force that causes earthquakes, during each 100 year period. Approximately every 100 to 150 years, the strain reaches a breaking point that results in a magnitude 8 level earthquake.
Historical Records: Few places in the world have such a well-documented history of past seismic activity. As a result, the frequency of earthquakes along the Nankai Trough is not just an estimate. Previously recorded earthquakes in the Nankai Trough include the Hakuho earthquake in 684 A.D, the Ninna earthquake in 887, the 1096 Eicho and 1099 Kangwa earthquakes, the Shohei (Kangan) earthquake in 1361, the Meio earthquake in 1498, the Keicho earthquake in 1605, the Hoei earthquake in 1707, the Ansei earthquake in 1854, and the 1944/1946 Showa earthquake.
Uneven Pattern of Destruction: In past Nankai Trough earthquakes, the entire Nankai Trough has been active at once, or the east and west have been active separately, showing the diversity in the way earthquakes occur.
Recent Observations of "Strain" on the Seafloor: Since 2006, the Japan Coast Guard has observed and routinely published seafloor deformation metrics at 15 points within the hypothesized epicenter of the Nankai Trough earthquake, from off the coast of Shizuoka near Tokyo to off the coast of Miyazaki in Kyushu. According to the results, it was found for the first time that strain had accumulated over a large area within the presumed epicenter zone. Strain was also found to have accumulated southwest of the epicenter of the Tokai earthquake and offshore of the epicenter of the Nankai earthquake that occurred in the 1940s. In the case of trench-type earthquakes such as the Nankai Trough earthquake, it is believed that the more strain that accumulates, the larger the earthquake or tsunami that will be generated.
Context: While the fear of a potential major earthquake and subsequent tsunami is never far from the minds of anyone living in Japan, the issue is especially front and center this week, which marks the 11th anniversary of the largest recorded earthquake in recent history.
It is also only about two months since the New Year's Day earthquake on the Noto Peninsula (能登半島地震). Significant delays in restoring lifelines to affected areas such as water supplies and ongoing concerns about the impact on the health of victims continue to make headlines in Japan. This latest “Big One” has brought into focus the issue of "secondary evacuation," in which people evacuate outside the disaster area. According to Ishikawa Prefecture, which is home to the epicenter, the peak number of secondary evacuees from the Noto Peninsula earthquake was 5,195 on February 17, 2024. Although many hotels and inns were secured as secondary evacuation centers, many of the earthquake victims were reluctant to leave their hometowns.
Why it matters: There is nothing in recorded history that comes close to the estimated extent of devastation that could be caused by the Nankai Trough earthquake and tsunami.
Magnitude: The Central Disaster Prevention Council (Cabinet Office) announced in 2012 that the Nankai Trough earthquake is likely to be at least magnitude 6-7 on the Japanese Seismic Intensity Scale.
Subsequent Tsunamis: According to Katsuya Yamori, a professor at Kyoto University's Disaster Prevention Research Institute who has led evacuation efforts in Shimanto City and Kuroshio City in Kochi Prefecture for 20 years, the Nankai Trough earthquake is likely to generate multiple tsunamis of up to 30 meters (approximately 100 feet) or more along the coast of Kochi Prefecture.
"The entire coastal area from Tokai (southwest of Tokyo) to Shikoku will be isolated, as happened recently on the Noto Peninsula. However, unlike Noto, the densely populated coastal areas of Osaka, Hyogo (Kobe) and Chugoku, which are expected to receive disaster victims (through secondary evacuation), are also likely to be affected by earthquakes and tsunamis." - Professor Katsuya Yamori
So we are talking about an event that would literally affect more than half of the country.
Human Loss: Worst-case scenarios put the potential loss of life at 330,000. For reference, the 1923 Kanto earthquake resulted in approximately 100,000 deaths in the Tokyo area.
Up to 8.8 million evacuees are expected to have their access to water cut off3. Of these, 8.1 million will likely need to be prevented from returning to their homes one month after the event, requiring a long-term response. To put this in perspective, the maximum number of evacuees after the Great East Japan earthquake was 346,987 people as of June 2012. To date, more than 29,000 people remain displaced 13 years later.
In the coastal areas along the Pacific Ocean expected to be affected by the Nankai Trough earthquake, how to care for elderly victims is a major concern. Elderly people with multiple cardiovascular diseases, such as heart failure, are at high risk of disaster-related death, and there is a limit to how long they can continue to survive as an evacuee.
Economic Impact: The Great East Japan earthquake dealt a severe blow to industrial and economic activities, particularly in the Tohoku region. According to the Small and Medium Enterprise Agency, there are approximately 800,000 businesses located in the areas affected by this tsunami and earthquake, and the total damage to commerce and industry has been estimated to be approximately 1,255.8 billion yen (US$8.5 billion) for the three prefectures of Tohoku4.
Damage to production and services from the massive Nankai Trough earthquake is estimated at 36.2 trillion yen ($246.3 billion), or about 7% of Japan's gross domestic product, affecting nearly 2/3 of all manufacturers in the country5.
In total water would be cut off to up to 35.7 million people, possibly for about a month. Electricity would be cut off to up to 29.3 million homes, and power outages due to damage to utility poles are likely to take approximately one to two weeks to restore.
What's next: While no one really knows, the big question is when will the Nankai Trough earthquake occur? The three recent earthquakes of Hoei, Ansei and Showa are considered to be Nankai Trough earthquakes based on the abundance of archival material. According to historical damage reports, the area surrounding the epicenter is considered to be "large" along the entire Nankai Trough including the Hyuga Sea during the Hoei earthquake, "medium" for the Ansei earthquake, and "small" for the Showa earthquake, which was limited to the Suruga Bay. The calculations are based on a scientific model called the "Time Prediction Model."
This model assumes that the interval between the next earthquake is proportional to the amount of slip from the previous earthquake. Based on this idea, the time until the next earthquake is longer after a large earthquake and shorter after a small earthquake. Thus, since it was 147 years after the relatively large Hoei earthquake and 90 years after the moderate Ansei earthquake, it means that the period until the next Nankai Trough earthquake since the Showa earthquake, which was small, may be less than 90 years. As of 2024, it has been about 80 years since that event. The probability of an earthquake occurring in the next 30 years has recently been revised from about 70% to 70-80%.
Thus, now it is time to be concerned.
Where it stands: How can we be better prepared? While everyone must ultimately take responsibility for themselves, it would be wise to learn what your city government is doing to prepare, too.
How to Prepare on Your Own: It is recommended that you pack your own personal earthquake supply kit. Here is what you need: enough water to last 3 days, non-perishable foods that are easy to prepare and eat without utensils, such as canned goods, dried fruit, nuts, and granola bars. Don't forget a can opener! Remember to pack any important medications and a flashlight. Don't forget extra batteries and a mobile phone charger. A battery-powered or hand-cranked radio, some cash, soap, hand sanitizer, feminine hygiene products, toilet paper, a whistle, blankets, and a dust mask may also come in handy. It is a good idea to keep copies of your passport, driver's license, insurance policies, and other important documents in a waterproof container, too.
What Your City Should Be Doing: Some communities are better prepared than others. One district in Yamori, Mie Prefecture, has built its own tsunami shelter on high ground. It is powered by solar panels in case regular power lines are down. It has a bathhouse, cooking facilities, and toilets that do not require running water. During each evacuation drill, the town’s elderly residents bring their personal belongings, such as clothes and stored food, in preparation for a long-term evacuation. They are not fooling around!
Kuroshio City has also begun to develop welfare shelters that can be self-sustaining in the event of an earthquake through "zero carbon" initiatives to promote the use of solar power generation and battery storage. Realistic disaster drills are routinely conducted, including the operation of evacuation centers and field medical stations using the batteries of electric vehicles (EVs). The city of Shimanto has also established a high-altitude nursing facility in the Okitsu coastal district that doubles as a self-sustaining welfare center.
What Your Sister City Should Be Doing: Even municipalities not expected to be directly affected by the Nankai Trough earthquake have developed innovative solutions to prepare to assist sister cities and receive evacuees.
Since 2013, Soja City, located in Okayama Prefecture on the Inland Sea (largely protected from the direct impact of a tsunami on the Pacific Ocean), has entered into agreements with nine cities and towns in Tokushima and Kochi prefectures that are likely to be directly in the path of the tsunami. Soja City is already planning to send medical teams of more than 200 people per week to evacuation centers for about a month after the earthquake.
"Our strength is that we will be able to respond quickly because we have a budget allocated every year along with plans already in place for dispatching personnel...We would like to respond with a certain degree of flexibility to the actual situation from the point of view of the disaster victims." - Soja City official
This proactive city has also made arrangements to receive disaster victims. Evacuees will be given free rooms in municipal housing. Upon arrival, each evacuated household will also receive a lump sum of 100,000 yen ($680) to be used as pocket money. A support allowance of up to 50,000 yen ($340) per month will also be provided for up to three months after the earthquake.
Similarly, since 2011, the city of Chizu, Tottori Prefecture (on the other side of the country along the coast of the Sea of Japan) has established a program called "Chizu City Evacuation Insurance." In the event of a disaster, including an earthquake in the Nankai Trough, policyholders are provided with shelter in the town and guaranteed meals in a guest house for one week. The premium is 10,000 yen ($68) per person per year, or 20,000 yen ($136) per year for a family of four. So far, most of the people who have signed up for this insurance program are from the Tokyo metropolitan area and the Kansai region (in and around Osaka).
Comment: Having lived in Japan for a total of more than 30 years at this point, I have experienced many earthquakes. However, I will never forget where I was at 2:46 p.m. on Monday, March 11, 2011, when the Great East Japan Earthquake struck the eastern part of the country. Although I was in the center of Tokyo at that time, 300 km (about 180 miles) from the epicenter, this giant earthquake, which lasted almost 20 seconds, was strong enough to knock you off your feet. Strong aftershocks continued for several days.
I had a group of clients at our office for a training program, and like me, many of them could not get home that night because the subways were shut down and the roads were virtually gridlocked. I spent the night in the office with our clients. It was a nerve-wracking afternoon and evening as mobile phone service was almost immediately overwhelmed. This made it very difficult to confirm that my own family - including two young sons who were in school at the time of the earthquake - were okay. We also struggled to locate and determine the status of all of our employees across the country - especially those who were based in the Tohoku region. In the weeks following the earthquake, I helped mobilize the delivery of medical supplies throughout the affected area.
I was in Japan when the magnitude 6.9 Great Hanshin earthquake struck in and around Kobe in the early morning hours of January 17, 1995, too. Although I was in Tokyo at the time, I was also present for the series of earthquakes in Kumamoto, including the magnitude 7.0 main shock that struck in the middle of the night on April 16, 2016. In both cases, I helped organize and implement relief efforts. So I have a lot of first-hand experience with major earthquakes in Japan.
While I have some idea of the extent of destruction likely to result from the upcoming Nankai Trough earthquake and tsunami, it would be on a scale beyond my previous experience.
The Japanese government at all levels seems to have prepared fairly robust contingency plans, but I still have concerns about whether such plans will be implemented effectively. Similar to how the U.S. military based in Japan provided a rapid response to 3/11, I have a feeling that American soldiers will likely play an important role as first responders.
While there is only so much you can do to prepare for the next "Big One," it is wise at least take the drills seriously and have some supplies on hand at home and at work. If you live in Japan, make time to visit a disaster center or mobile event that offers a free "ride" in an earthquake simulator. It will literally shake you to your bones and demonstrate just how powerful a large earthquake can be. The most memorable experience, however, was a simulation of escaping a smoke-filled office after the lights went out and only a few exit signs were visible to guide people to safety.
One curious development in the aftermath of the three major earthquakes mentioned above is that the fallout continues to fuel a boom in the popularity of minivans - including lightweight "kei cars" - that can be used as campers. In fact, such "mobile bunkers" were used by many after the latest earthquake on the Hokuriku Peninsula just a few months ago. Lately, I have been thinking that such a vehicle might be a good investment.
As for the Nankai Trough earthquake, it is not a question of if, but when. Despite the best planning, this megaquake will cause tremendous damage and loss of life. Therefore, everyone living in Japan should be aware of this future threat and seriously consider what can be done to mitigate the risk.
Links to Japanese Sources: https://news.yahoo.co.jp/articles/6d68a3c3e7a3fbcc77d8be404e61e29d292aceac, https://news.ntv.co.jp/category/society/330899, and https://news.yahoo.co.jp/expert/articles/47bfe923c221275025530446765bbb18af6d834c.
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Tsunami = tidal wave
Not including 3,802 deaths from related illnesses or stress-related suicides.
避難者数の推移(所在都道府県別)、全国の避難者の数(所在都道府県別・所在施設別の数)[平成23年度~令和4年度]、復興庁 (Reconstruction Agency)
東日本大震災復興政策10年間の振り返り、6章、産業・生業の再生、復興庁
防災・減災、国土強靱化~中長期的な視点からの問題提起~、国土交通省
養老孟司先生によれば2038年に起こる予定です。東京は震度5弱、東南海地震と西南海地震の2回、1度に起こるようです。新幹線は維持できないようなので、車があったほうが便利ですかね。
How hard it must have been not to be able to immediately communicate with your sons. My daughters were already grown in 2011 and living outside Japan, so the worry went in the opposite direction, with them concerned for me. But after the Great Hanshin Earthquake, when my daughters were still young, I had a terrible recurring dream in which a major earthquake struck and I was trying to get back from Tokyo to find them.