❖ After a 7.1-magnitude earthquake shook the southern Japan, the country’s meteorological agency issued its first-ever “megaquake advisory”

❖ The warning said the likelihood of strong shaking and large tsunamis is higher than normal on the Nankai Trough.

❖ Nankai Trough is a 900 km long subduction zone along Japan’s southwest Pacific coast.

❖ The trough has produced large earthquakes roughly every 100 to 150 years.

❖ These tremors usually come in pairs, with the second often rupturing in the subsequent two years.

❖ The most recent “twin” earthquakes took place in 1944 and 1946.

❖ This advisory by the Japan’s meteorological agency was just a warning not a prediction.