What Deep focus earthquakes are associated with what prominent ocean floor feature?

Deep-focus earthquakes are associated with the subduction zones of oceanic plates. These zones occur where one tectonic plate is forced to move beneath another plate. The deep-focus earthquakes are caused by the brittle failure of the subducted oceanic plate as it is pushed down into the mantle. The earthquakes can occur at depths of up to 700 km, and they are often accompanied by large tsunamis.