Accurate models of the distribution of heterogeneities in the Earth's mantle, especially of subduction zones, are crucial for our understanding of the composition and dynamics of the Earth. Here we present broad-band (BB) seismograms with P-waves reflected at the subduction zone under southern Japan at about 84¿ distance from German Regional Seismic Network. The earthquakes occurred in the Mariana Islands region at 100¿ to 105¿ distance. Array techniques allow the separation of this wave with an asymmetric path (P1P2) from reflections and conversions under the source, the receivers and the midpoint between the source and the receivers. Our observation demonstrates that subduction zones can act as strong seismic reflectors and can be mapped with a depth resolution of ¿20 km with BB arrays at teleseismic distances. The analysis of such data will help to derive a more detailed picture of the structure of the Earth's mantle. ¿ American Geophysical Union 1996