High-resolution image of the oceanic Moho in the subductirng Nazca plate from P-S converted waves

Short-period P - S converted waves outline the oceanic Moho of the descendi ng Nazca plate in northern Chile at 24 degreesS. Comparison with hypocentra l locations obtained with temporary local seismic networks show that earthq uakes inside the subducting oceanic lithosphere of the Nazca plate are loca ted predominantly in the oceanic crust at depths between 70 and 120 km, and probably in the upper mantle at depths below 120 km. The results suggest t hat dehydration embrittlement as mechanism for intermediate-depth earthquak es is active both in the former oceanic crust and upper mantle of subductin g lithosphere.