Nankai Trough Megaquake Threatens Japan: What You Need To Know About The 3 Lakh Casualty Warning

According to new government estimates, Japan is expecting a megaquake in the Nankai Trough. Scroll down to learn more about this earthquake which might take lakhs of lives.

Anukriti Srivastava
Editorial
Updated - 2025-04-01, 17:00 IST

According to new government estimates, a megaquake in Japan could result in up to 298,000 deaths and $2 trillion in damages. The likelihood of such an event occurring in the next 30 years is now believed to be 75-82%. The megaquakes in the Nankai Trough have struck every 100 to 200 years, with the most recent occurring in 1946. Scroll down to learn more about this disaster.

Megaquake In Japan

A Megaquake is the most powerful earthquake with magnitude 8 or more, leading to loss of lives and severe devastation. A “Megaquake” and subsequent tsunami is expected to cause as many as 298,000 deaths in Japan and cause damage up to $2 trillion, as estimated by the government on Monday. The warning follows a magnitude 7.1 jolt in Southern Japan which injured 14 people in 2024. The Japanese government issued its first advisory in August 2024 for a potential megaquake along with the Nankai Trough.

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Why Is Tokyo Fearing A Megaquake?

The Nankai Trough is a 900-kilometre undersea fault stretching from Shizuoka to Kyushu. The probability of producing a magnitude 8-9 quake within the next 30 years is 70-80%. According to historical patterns, megaquakes occur in Japan every 100-200 years with the last major event taking place in 1946. A rupture could trigger tsunamis reaching 30-34 metres within minutes devastating coastal regions like Shizuoka, Kochi, and Wakayama. Tokyo’s urgency stems from the Trough’s volatile tectonic activity where the Philippines Sea Plate subducts beneath the Eurasian plate, storing a lot of energy that is capable of causing an earthquake up to magnitude 9.1.

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What Makes Nankai Dangerous?

The Nankai Trough’s tectonic strain has been accumulating over centuries posing a threat to cause sequential megaquakes. Research conducted by Tohoku and Kyoto Universities warns that a magnitude 7+ earthquake can lead to follow-up tremors 100-3600 times higher than normal within a week. According to the Cabinet Office’s disaster management working group, up to 215,000 people could die in a tsunami, 73,000 due to buildings collapsing and 9000 in fires. However, the estimated megaquake can lead to 323,000 deaths, as predicted.

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