Lateral variation in the structure of the upper mantle beneath Eurasia

A travel-time curve for seismic rays bottoming within the upper mantle beneath Western Russia and recorded at the NORSAR array is substantially different from a curve for rays bottoming beneath Southern and Central Europe, recorded at the NORSAR and Eskdalemuir arrays. This difference is interpreted in terms of a laterally varying velocity structure to a depth of approximately 500 km beneath the two regions.