Nankai Trough

About Nankai Trough: 

• It is a “subduction zone” between two tectonic plates in the Pacific Ocean, where massive earthquakes have hit in the past.
• This underwater subduction zone (nearly 900 km long) where the Eurasian Plate collides with the Philippine Sea Plate, pushing the latter under the former and into the Earth’s mantle.
• Location: It runs from Shizuoka, west of Tokyo, to the southern tip of Kyushu Island.
• It has been the site of destructive quakes of magnitude eight or nine every century or two.
• These so-called “megathrust quakes”, which often occur in pairs, have been known to unleash dangerous tsunamis along Japan’s southern coast.

What is the Subduction Zone?

• It is a spot where two of the planet's tectonic plates collide and one dives, or subducts, beneath the other.
• Tectonic plates are pieces of the Earth’s rigid outer layer that slowly move across the planet's surface over millions of years.
  • This is the main tenet of plate tectonics, the theory that portions of Earth's shell glide over the lower mantle, taking continents with them.
• Subduction zones occur in a horseshoe shape around the edge of the Pacific Ocean, offshore of the USA, Canada, Russia, Japan, and Indonesia, and down to New Zealand and the southern edge of South America called the "Ring of Fire,”
• These subduction zones comprise “the most seismically and volcanically active zone in the world, responsible for more than 80% of the world's biggest earthquakes and most of the planet’s active volcanoes.

Q1: What is an Earthquake?

An earthquake is the shaking or trembling of the earth's surface caused by a sudden release of energy from the interior of the earth.

Source: Japan issues its first-ever ‘megaquake advisory’: What does it mean?