This research is to analyze existing digital seismic data sets for further evidence of a strong P-velocity anomaly in the lower mantle beneath the northern Soviet Union and, if possible, to map its spatial extent. Although considerable SH data show evidence of anomalous structure up to 350 km above the core- mantle boundary, to this date only European WWSSN data and the GRF array have been searched successfully to find the P-wave analog produced by such an anomaly. The results should give information on what kind of structure is giving rise to the anomalous observations which can, in turn, constrain dynamical models of the mantle and core.
