Context

Recently, Japan issued the first 'megaquake warning' of a powerful earthquake and large tsunami over the Nankai Trough (a subduction zone).

About the Nankai Trough

• It is an underwater subduction zone marked by the subduction of several geological units of the Philippine Sea Plate (Kyushu-Palau Ridge, Shikoku Basin, Kinan Seamount Chain and Izu-Bonin Arc) beneath the Eurasian Plate southwest of Japan.
• This causes tectonic stress to accumulate, which can cause megaquakes - earthquakes with a magnitude greater than 8.
• It is located between Suruga Bay in central Japan and the Hyuganada Sea in Kyushu to the south.