Teleseismic recordings of several seismograph stations are processed with the aid of the S receiver function technique <Farra and Vinnik, 2000>. The data provide evidence of a strong reduction of S velocity at a depth around 360 km (station BOSA) and 280--300 km (station LBTB) in the East of southern Africa. A similar feature is found in the Tunguska basin of the Siberian platform from the recordings of station NRIL. In both regions large volumes of flood basalts have been erupted 190--180 Ma and 250 Ma ago, respectively. The coincidence suggests a causal relation between the two phenomena. This relation implies that the low-velocity anomalies migrate with the plates.