The Nankai Trough Earthquake: In-Depth Analysis of the Past, Present, and Future
Japan, a nation located on the boundary of tectonic plates, faces constant threats from earthquakes and tsunamis. Among these, the Nankai Trough earthquake is one of the most destructive natural disasters in Japan’s history. It occurs approximately every 100 to 150 years, causing massive damage. Recently, the Japanese government and academia have estimated an 80% likelihood of its occurrence within the next 30 years, with the worst-case scenario projecting 300,000 fatalities and economic damages of up to ¥1,400 trillion (approximately 1,369.6 trillion KRW). Additionally, the prophecy in the manga "The Future I Saw" by Tatsuki Ryo, predicting a major disaster in July 2025, has exacerbated public anxiety. This article will delve into the history, potential damage, occurrence likelihood, prophetic claims, and impact on travel to Japan, thoroughly examining this complex issue.
1. The Historical Record and Damage of the Nankai Earthquake
The Nankai Trough stretches for about 800 kilometers from Shizuoka Prefecture in central Japan to the southern part of Shikoku and the eastern coast of Kyushu. The subduction of the Philippine Sea Plate beneath the Eurasian Plate accumulates energy, which is periodically released, triggering massive earthquakes of magnitude 8 to 9. Historically, some major events include:
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1707 Hōei Earthquake (M8.6): A massive earthquake that caused around 20,000 fatalities due to the tsunami and also triggered the eruption of Mount Fuji (Hōei Eruption), which caused additional ash damage in Edo (now Tokyo).
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1854 Ansei Earthquake (M8.4): Two major quakes struck on December 23 and 24, resulting in the deaths of approximately 3,000 to 5,000 people.
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1944 Shōwa Tonankai Earthquake (M8.1) and 1946 Shōwa Nankai Earthquake (M8.1): These earthquakes claimed about 1,200 and 1,300 lives, respectively. Due to World War II, recovery efforts were hindered.
These earthquakes, accompanied by tsunamis, devastated coastal regions. The Hōei Earthquake, in particular, remains the most significant in Japanese history, highlighting the catastrophic potential of a combined earthquake event. Records indicate that the Nankai Trough releases energy every 100-200 years, with combined earthquakes (involving the Nankai, Tonankai, Tokai, and other regions) leading to catastrophic consequences.
2. Likelihood of Occurrence and Estimated Damage of the Nankai Earthquake
Likelihood of Occurrence
The Japanese government and the Earthquake Research Promotion Headquarters estimate an 80% chance of a Nankai Trough earthquake occurring within the next 30 years. This estimation is based on the fact that approximately 80 years have passed since the last major earthquake in 1946, and energy has accumulated along the fault line. Additionally, recent seismic activity, such as the magnitude 6.9–7.1 earthquakes off the coast of Miyazaki Prefecture (August 2024 and January 2025), has been interpreted as a possible precursor. However, scholars argue that these smaller quakes are not directly linked to the Nankai Trough earthquake, and accurate predictions remain impossible.
The Nankai Trough is divided into four regions: the Higanada, Nankai, Tonankai, and Tokai zones. Earthquakes may occur in these regions either individually or simultaneously. The worst-case scenario would involve a massive 9.0 magnitude earthquake, similar to the 2011 Tōhoku Earthquake (M9.0).
Estimated Damage
According to the Japanese Cabinet Office's expert review (released March 2025), the following damage is expected:
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Fatalities: Up to 298,000 people, most from the tsunami.
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Displaced People: 12.3 million.
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Building Damage: 2.35 million buildings destroyed.
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Economic Losses: Direct losses of ¥225 trillion (approximately ¥2,223 trillion KRW) and indirect losses reaching ¥292.3 trillion (approximately ¥2,889 trillion KRW), which is nearly half of Japan's GDP (approximately ¥609 trillion).
The Japan Society of Civil Engineers warns that in the event of a combined earthquake, the economic damage could exceed ¥1,410 trillion (approximately ¥1,369.6 trillion KRW), potentially collapsing Japan's economy and leading to a dramatic fall in global economic standing. The region surrounding the Nankai Trough is also home to several nuclear power plants, raising concerns about potential radiation leaks.
Potential Impact on South Korea
There is a possibility of indirect effects on South Korea, with seismic tremors reaching the southern coast of Jeju and Busan at levels of magnitude 3 to 4, and possibly even triggering tsunami waves along the southeastern coast. However, due to the geological structure of the Korean Peninsula, direct damage is likely to be limited.
Mount Fuji Eruption Potential
Another concern is that the Nankai Earthquake could trigger an eruption of Mount Fuji, similar to the Hōei eruption following the 1707 earthquake. Mount Fuji has been dormant for over 300 years, which is the longest period of dormancy in its 5,000-year history. If an eruption occurs, volcanic ash could reach Tokyo, adding further damage to the region.
3. Tatsuki Ryo’s Prophecy and Public Reaction
Tatsuki Ryo and "The Future I Saw"
Tatsuki Ryo, a Japanese manga artist born in 1954, gained attention for his book "The Future I Saw" (first published in 1999), in which he made predictions based on prophetic dreams. Initially, the book did not receive much attention, but after the 2011 Tōhoku earthquake (M9.0), which Ryo had predicted in the book with the phrase "March 2011 disaster," it gained widespread recognition. He was also credited with foreseeing other events, including the death of Freddie Mercury (1991) and the COVID-19 pandemic (2020).
In the 2021 revised edition of "The Future I Saw", Ryo predicted a colossal disaster to strike Japan and the Pacific coastal areas on July 5, 2025. According to his prophecy:
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A massive tsunami, three times the height of the 2011 Tōhoku tsunami, will be caused by a volcanic eruption in the Philippine Sea.
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One-third to one-quarter of the Japanese archipelago's Pacific coastline will be submerged.
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Major geological changes will occur, connecting Hong Kong, Taiwan, and the Philippines.
Ryo added that this catastrophe will be followed by the arrival of an "age of spirituality," where the world will transform into a harmonious and enlightened place.
Public Reaction to the Prophecy
The prophecy by Tatsuki Ryo has heightened public anxiety for several reasons:
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Accuracy of Past Predictions: Ryo's previous accurate predictions, such as the 2011 Tōhoku earthquake and the COVID-19 pandemic, lend credibility to his forecast, making people more likely to take his latest prophecy seriously.
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The Real Threat of the Nankai Earthquake: The 80% likelihood of the Nankai Trough earthquake, coupled with recent seismic activity, aligns with Ryo's prophecy, amplifying fears.
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Spread via Social Media: The prophecy has spread rapidly on platforms like X (formerly Twitter) and YouTube, leading to cancellations of travel bookings and real estate purchases, especially in Hong Kong and China.
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Psychological Impact: Japan's history of frequent earthquakes and the trauma from the 2011 Tōhoku disaster has made the population more susceptible to fear, with Ryo’s prophecy exacerbating this anxiety.
However, there are also skeptics. Not all of Ryo’s predictions have come true, and some events have either occurred at different times or not at all. The Japanese Association for the Skeptical Investigation of Supernatural Phenomena has dismissed Ryo's predictions as mere coincidences. Moreover, Ryo himself has cautioned against excessive fear, stating that his aim is to encourage disaster preparedness rather than panic.
4. Impact on Travel to Japan
The Ripple Effect of the Prophecy
The prophecy and the warnings of the Nankai Trough earthquake have had a significant impact on Japan’s tourism industry. For instance, in Hong Kong, the "July disaster prophecy" has led to an increase in travel cancellations, with Greater Bay Airlines cutting flights to Sendai and Tokushima. The Chinese Embassy has advised its citizens to avoid traveling to Japan and cautioned against purchasing real estate there.
In South Korea, fears about the potential "July 2025 disaster" have also spread through social media, with some people even urging for cancellations of planned trips to Japan. However, travel agencies in Korea (such as Hana Tour and Klook) have stated that the cancellation rate remains similar to previous years, and no significant changes have been observed.
Expert Opinion
Korean experts stress the importance of preparedness rather than succumbing to excessive fear. Professor Kim Seung-seop from Chungnam University stated, "Although the Nankai Trough poses a significant threat to Japan, South Korea’s geological structure suggests that we are unlikely to suffer major damage. However, preparation for tsunamis is still essential." The Japanese government also reiterated that predicting earthquakes scientifically remains impossible and urged the public to rely on official information.
5. Japanese Government and Society’s Response
The Japanese government has implemented several measures to prepare for the Nankai Trough earthquake:
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Revised Disaster Plans: Aiming to reduce casualties by 80% and building damage by 60%, the government is pursuing 134 disaster mitigation measures.
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Seismic Reinforcement: The government plans to invest ¥40 trillion in reinforcing infrastructure in western Japan and improving road networks.
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Psychological Support: The government is expanding its Disaster Psychiatric Assistance Teams (DPAT) to address the psychological needs of up to 220,000 people affected by the disaster.
While the public is concerned due to the prophecy and foreshocks, some individuals are taking proactive steps, such as relocating to Hokkaido. However, there is also strong criticism against allowing unscientific prophecies to stir unnecessary panic.
6. Conclusion: The Importance of Balance in Preparedness
The Nankai Trough earthquake is an unavoidable threat rooted in Japan’s geological history. The devastation of past events and the recent seismic activity indicate that this danger is not distant. While Tatsuki Ryo’s prophecy lacks scientific evidence, it has stirred public anxiety and underscored the importance of disaster preparedness. However, excessive fear can cloud rational judgment.
For those planning to travel to Japan, it is important to refer to official sources and avoid overreacting to uncertain prophecies. South Korea faces limited direct risks, but basic preparations, such as tsunami readiness, are advisable. Ultimately, the Nankai Trough earthquake serves as a reminder of humanity’s vulnerability in the face of nature and the life-saving value of preparedness.
