Why do earthquakes happen at destructive plate margins?

At destructive plate margins, oceanic crust subducts beneath continental crust. In this zone of subduction a lot of friction is created as the plates move alongside each other. Over time, the build up of friction will become so great that the plates reach a breaking point in which the pressure is released in the form of an earthquake. The zone in which earthquakes occur within destructive plate margins is called the Benioff zone.