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When it comes to earthquakes, certain parts of the world are at higher risk than others. Given that earthquakes are caused by friction between slow-moving tectonic plates, the parts of the world that are located on a tectonic plate boundary are at particularly high risk.
One such high-risk zone is the Nankai Trough, which is located off the southwest coast of Japan. Experts predict that we could be due a megaquake in this region very soon, and it has the potential to cause huge destruction.
Check out this gallery to find out more.
On the afternoon of August 8, 2024, a magnitude 7.1 earthquake hit southwest Japan, rattling the city of Kyushu and vigorously shaking the city of Nichinan.
Triggered at a depth of 37 kilometers (23 miles) below the Earth’s surface, the quake caught the attention of seismologists at the Japan Meteorological Agency (JMA).
The seismologists called a special meeting, where they discussed whether the earthquake could be an indication of something bigger to come.
In particular, they were concerned about a massive earthquake occurring along the Nankai Trough, which runs below the sea south of Shikoku and western Honshu.
Later the same day, the JMA issued its first ever megaquake alert. Residents of risk zones were encouraged to review evacuation procedures and stay vigilant for a week.
In the end, a megaquake did not occur. Indeed, according to the JMA, the chance of a bigger earthquake after a magnitude seven tremor is around one in several hundred.
The event did serve as a reminder, however, that Japan is one of the world’s most earthquake-prone countries.
Indeed, it sits on an arc of volcanoes and oceanic trenches known as the "Ring of Fire." In 2011, for example, more than 15,000 people were killed in a magnitude 9 quake.
The 2011 earthquake hit northeast Japan and triggered a tsunami, as well as causing triple reactor meltdowns at a nuclear power plant.
One of the highest-risk areas for earthquakes in Japan is the Nankai Trough, a submarine trough located off the country’s southwest coast. It runs for approximately 900 kilometers (600 miles).
The Nankai Trough marks a subduction zone, where the Philippine Sea Plate is subducting under the Eurasian plate.
As per recorded history, the tectonic strains that accumulate as a result of this subduction result in a megaquake roughly every 100 to 150 years.
It has been around 80 years since the last significant shakes in the region. The Tonankai earthquake (1946) and the Nankai earthquake (1946) had magnitudes of 7.9 and 8.0, respectively.
According to the Japanese government, there is an 80-90% likelihood that a megaquake will occur along the Nankai Trough in the next 30 years.
A megaquake along the Nankai Trough has the potential to cause devastating damage. The maximum measurable tremors would be felt in areas from central Shizuoka to southwestern Miyazaki.
Within minutes after the quake, tsunami waves of up to 30 meters (98 feet) could reach Japan’s Pacific coasts.
The exact timing and size of the tsunami waves would depend on the epicenter of the earthquake and the tidal situation at the time.
In 2019, the government’s Central Disaster Prevention Council released projections about the number of lives that may be taken by a megaquake and ensuing tsunami.
According to the projections, there could be as many as 230,000 people dead or missing as the result of such an event.
In a worst-case scenario, nearly 2.1 million buildings in the affected region could be burned to the ground or otherwise destroyed.
According to Reuters, the economic damage to the country could be as much as 220 trillion yen (US$1.5 trillion), which equals more than a third of Japan’s annual GDP.
There would be a long-lasting impact on infrastructure and long-term disruption to supply chains that are needed to produce key Japanese products, such as cars.
As previously mentioned, Japan has a long history of megaquakes along the Nankai Trough. The earliest recorded megaquake in the region was in 684 CE.
With an epicenter spanning from today’s Kochi Prefecture to Wakayama, records suggest that this magnitude 8.3 quake caused landslides and overflowing rivers.
There were reports of numerous buildings, temples, and shrines being destroyed, as well as many humans and livestock being losing their lives.
More recently, there was a pair of significant earthquakes that struck the region in the 1940s. The first had a magnitude of 7.9 and struck in 1944, offshore from the Kii Peninsula to the Enshunada Sea.
Two years later, the second quake, which had a magnitude of 8.0, hit the Nankai fault to the west, offshore from the Kii Peninsula and along the Shikoku coast.
The 1944 earthquake caused severe damage to the Shizuoka, Aichi, Gifu, and Mie prefectures. The 1946 quake caused a huge tsunami that struck shorelines between the Boso Peninsula and Kyushu.
Interestingly, this was not the first time that two megaquakes struck the region in quick succession–the same thing happened in 1096 and 1099.
Sources: (Reuters) (Nippon.com)
See also: Early warning signs of earthquakes, tsunamis, and other disasters
What is the Nankai Trough, and why is it important?
The Japanese region prone to earthquakes
LIFESTYLE Earthquakes
When it comes to earthquakes, certain parts of the world are at higher risk than others. Given that earthquakes are caused by friction between slow-moving tectonic plates, the parts of the world that are located on a tectonic plate boundary are at particularly high risk.
One such high-risk zone is the Nankai Trough, which is located off the southwest coast of Japan. Experts predict that we could be due a megaquake in this region very soon, and it has the potential to cause huge destruction.
Check out this gallery to find out more.