October 18, 2021
Trench-type earthquakes, similar names in English-speaking countries, are megathrust earthquakes. These earthquakes at plate boundaries are so powerful that they usually exceed the magnitude of the moment M9.0. Since all supermassive earthquakes greater than M9.0 since the 1900's have been trench-type earthquakes, strong earthquakes with large moment magnitudes among trench-type earthquakes are often referred to as giant earthquakes. A representative mega-earthquake is the 2011 M9.1 earthquake in the Pacific Ocean in the Tohoku region.