<P> A deep - focus earthquake in seismology (also called a plutonic earthquake) is an earthquake with a hypocenter depth exceeding 300 km . They occur almost exclusively at oceanic - continental convergent boundaries in association with subducted oceanic lithosphere . They occur along a dipping tabular zone beneath the subduction zone known as the Wadati--Benioff zone . </P> <P> Preliminary evidence for the existence of deep - focus earthquakes was first brought to the attention of the scientific community in 1922 by Herbert Hall Turner . In 1928, Kiyoo Wadati proved the existence of earthquakes occurring well beneath the lithosphere, dispelling the notion that earthquakes occur only with shallow focal depths . </P>

Where do earthquakes that have deep foci usually occur