Friction prevents tectonic plates from slipping against each other

Accumulated energy is eventually released forcefully.

Interplate megathrust earthquakes have inflicted catastrophic damage on human society. Such an earthquake is predicted to occur in the near future along the Nankai Trough off southwestern Japan — an economically active and densely populated area in which megathrust earthquakes have already occurred.

Megathrust earthquakes are the result of a plate-subduction mechanism and occur at slip-deficit regions (also known as ‘coupling’ regions), where friction prevents plates from slipping against each other and the accumulated energy is eventually released forcefully.

Excerpted from Nature.