Upper lithospheric structure in the central Fennoscandian shield: constraints from P- and S-wave velocity models and Vp/Vs ratio distribution of the BALTIC wide-angle seismic profile

The paper presents an analysis of the crust and upper mantle structure in the central Fennoscandian shield based on new P- and S-wave 2D velocity models of the BALTIC wide-angle reflection and refraction profiles. Using reprocessing of the old data, new P- and S-wave velocity models and V P /V S ratio distribution were developed. Moving from SW to NE, the thickness of the crust varies strongly, from ∼36 km to extremely thick, 58–64 km, crossing Wiborg rapakivi massif, Saimaa and Outokumpu areas, and Eastern Finland complex. Based on the lateral variations of V P , V P /V S and thickness of the crust, three main blocks of the crust and upper mantle were distinguished from SW to NE: southwestern, associated with Wiborg rapakivi massif; the central, having the highest thickness of the crust; and the northeastern, not well documented, with Archaean basement.