Upper mantle converted waves beneath the Nars array

Several registrations of teleseismic events on the NARS array show a phase which can be identified as a P to S conversion at the 670‐km discontinuity beneath western Europe. Variations in the amplitude and arrival time of the so‐called Ps phase are observed for different azimuths. A single station/multiple event stacking technique was applied to the data to determine the consistency of the phase. The results are indicative of amplitude, arrival time, and slowness variations of the converted phase on a local scale. These observations are most logically explained by a model with depth variations of the 670‐km discontinuity of the order of 20 km over a distance of 200 km.