Earthquake energy released at various depths

Most energy of earthquakes is released in crustal layers above the Mohorovicic discontinuity. In the circum-Pacific and Alpide belts, the only zones where foci below 60± km are known, the average annual energy released in earthquakes decreases downward to a minimum near 300 km depth. Except for secondary maxima near 350 km in the Japanese area and near 400 km (from a single large shock) in the Tonga-Kermadec belt, the energy release in belts with very deep foci remains relatively small down to 500± km and increases to a secondary maximum between 550 and 650 km. Below 650 km the energy release decreases rapidly to zero below 720± km.