NANKAI TROUGH (Syllabus: GS Paper 1 - Geography)

Context: Following a 7.1-magnitude earthquake in southern Japan, the country’s meteorological agency issued its first-ever "megaquake advisory," warning of increased likelihood of strong shaking and large tsunamis on the Nankai Trough.

Nankai Trough

• About: It is an underwater subduction zone, approximately 900 km long, where the Eurasian Plate collides with the Philippine Sea Plate.
• Tectonic Stress: The collision causes the Philippine Sea Plate to be pushed under the Eurasian Plate and into the Earth’s mantle, leading to the accumulation of tectonic stress.
• Megaquakes: This tectonic stress can result in a megaquake, which is an earthquake with a magnitude larger than 8.
• Historical Frequency: The Nankai Trough has historically produced large earthquakes approximately every 100 to 150 years.
• Twin Earthquakes: Earthquakes in this region often occur in pairs, with the second earthquake usually happening within two years of the first. The last pair occurred in 1944 and 1946.
• Risk Assessment: Japan’s Earthquake Research Committee stated in January 2022 that there is a 70% probability of a magnitude 8-9 megaquake occurring along the Nankai Trough within the next 30 years.