Descent of Lithosphere beneath New Hebrides, Tonga-Fiji and New Zealand: Evidence for Detached Slabs

Abstract

Study of seismic wave propagation in the mantle beneath the New Hebrides island arc shows that the remarkable gap in seismic activity between deep and intermediate depth earthquakes at the northern part of the arc corresponds to a gap in the lithospheric slab descending beneath the arc: the deep earthquakes mark a detached piece of lithosphere. Although observations for New Zealand deep earthquakes are ambiguous, other evidence suggests the detachment of lithosphere beneath New Zealand.