Evidence for transformational faulting from a deep double seismic zone in Tonga

The Tonga subduction zone has a double seismic zone at a depth of 350-460 km as revealed in a relocation and three dimensional visualization of earthquake positions using the hypocentroidal decomposition technique. Intermediate depths of 70-200 km suggested the presence of double seismic regions in subduction zones. Waveform analysis demonstrated in-plane tension in the upper region and in-plane compression in the lower region.