Epicenters of intermediate-depth events located by the ISC, taken together with focal depths determined from the reflected phase pP, define a double-planed seismic zone beneath northern Chile and northwestern Argentina. The lower zone of seismicity, however, is the result of a systematic misidentification of sP as pP at many North American seismograph stations. The lower seismic plane consists of 14 earthquakes located between 22¿ and 24.5¿ S that occurred between 1964 and 1984. Depths calculated from pP arrival times reported to the ISC are heavily biased by the abundance of reports from high-gain stations in western North America. Reports form these stations place the lower zone events at 125-150km depth, 35-45km below the main Wadati-Benioff zone. Short-period seismograms produced by the lower zone earthquakes at North American stations show only one clear reflected phase following P, which is often incorrectly identified as pP. Our identification of this phase as sP results in a shallower depth determination that is in agreement with pP and sP arrival time reports from stations in Africa and Southern Europe. The absence of a strong pP phase from North American records for the 14 events can be explained by the proximity of its take-off angle to a nodal plane on the focal sphere. The majority of intermediate depth events in the region lie in the upper plane; these earthquakes do produce recognizable pP phases. Hence, no clear evidence exists for a double-planed seismic zone in this region.