Crustal structure along the Blue Road Profile in northern Scandinavia

Abstract

Abstract Crustal velocity-depth models are presented from a deep seismic sounding profile across the Scandinavian peninsula. The Pg phases are influenced by local basement geology. Pg velocities as high as 6.4 km/s have been recorded over nappe units in the Caledonides. Along the Fennoscandian Shield part of the profile the velocity increases from about 5.4 to 6.0 km/s in an uppermost zone of the earth's crust, which is about 2 km thick. Faults have been detected in the uppermost part of the crust, one of which coincides with a shear zone deduced from purely geological reasoning. Velocity reversals in the Caledonides are invoked to explain the recorded data from the uppermost part of the crust. No velocity reversals have been detected along the Fennoscandian Shield part of the profile. A velocity increase from 6.3 to 6.7 km/s in a transition zone of some kilometres thickness divides the crust into an upper and lower part. The depth of the transition zone increases from 13 to 27 km below the eastern and we...