Short-period P--S converted waves outline the oceanic Moho of the descending Nazca plate in northern Chile at 24 ¿S. Comparison with hypocentral locations obtained with temporary local seismic networks show that earthquakes inside the subducting oceanic lithosphere of the Nazca plate are located 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 that dehydration embrittlement as mechanism for intermediate-depth earthquakes is active both in the former oceanic crust and upper mantle of subducting lithosphere. ¿ 2000 American Geophysical Union