What's Nankai Trough? Ocean-floor trench at risk of 9-magnitude megaquake
What's the story
Japan's government has warned of a potential catastrophic earthquake in the Nankai Trough region in a report released on Monday.
The geological area near Japan's Pacific coast is one of the most seismically active regions in the world.
The report claims such an event could cause tsunamis and loss of life on a massive scale, possibly even up to 300,000 fatalities.
Financial fallout
Economic impact of potential megaquake
A major earthquake in the Nankai Trough could cause losses of $1.81 trillion (about ₹149 lakh crore), the report estimates.
This would be nearly half of Japan's total GDP and a massive increase from earlier estimates.
The revised projection considers inflationary pressures and updated data on terrain and ground conditions, which widened the predicted flood zones.
Geological background
Nankai Trough: A history of seismic activity
According to Japanese official projections, the Nankai Trough is 70-80% likely to produce a magnitude 8-9 earthquake over the next 30 years.
Megaquakes have been recorded here every 100-200 years.
A rupture can cause tsunamis of 30-34 meters in minutes, damaging coastal prefectures such as Shizuoka, Kochi, and Wakayama.
The last major earthquake in the region was in 1946, with a preliminary magnitude of 8.0. It killed over 1,300 people.
Seismic risk
Nankai Trough: A potential trigger for megaquakes
The Nankai Trough, an 800-kilometer (500-mile) undersea trench that runs from Shizuoka, west of Tokyo, to the southern point of Kyushu island, is where two tectonic plates meet.
Along the fault, the Philippine Sea oceanic tectonic plate is "subducting" - or gradually slipping - beneath the continental plate that Japan rests on.
As they travel, the plates become locked, storing enormous quantities of energy that is released when they break free, potentially causing large earthquakes or megaquakes.
Preparedness measures
Japan's response to increased seismic risk
Given the threat, the Japan Meteorological Agency issued a megaquake advisory last year.
Subsequently, the Fire and Disaster Management Agency directed 707 municipalities vulnerable to a Nankai Trough earthquake to re-evaluate response strategies and evacuation plans.
Experts have appealed to the public not to panic but to carry on with daily life while preparing for emergencies by stocking up on essentials and talking about evacuation plans with family members.