The deep seismic sounding BALTIC was conducted in 1982 to investigate the crustal structure of the Fennoscandian shield (Luosto et al. 1990). The 560 km (including Kostomuksha shots, main part 430 km) long survey profile runs northeast from the Gulf of Finland to Kostomuksha, Russia. Seismic sources were explosions shot at eight different shot points at sea, in shallow lakes and in a quarry. These shots were recorded by 48 seismic stations along the profile at an average receiver spacing of 2 km. The stations included 36 three-component stations: 16 “MARS 66”, 10 “ASS”, 10 “SN-PCM80” and 12 six-channel stations: 10 “Taiga-2” and 2 “SN-PCM-80”. The profile crosses the Wiborg rapakivi batholith, the Svecokarelian geosynclinal complex and the Archean basement complex in southeastern Finland. Two-dimensional crustal velocity models of the profile have been constructed by a trial-and-error ray tracing method. The model displays variability of 40 to more than 60 km in crustal thickness, the thickest crust being situated in the border region of the Svecofennian and Karelian domains. Three different velocity models are available for the BALTIC profile. The original P-wave velocity model was constructed by Luosto et al. (1990). New P- and S-wave models were published later by Janik (2010). Wide-angle P-wave sections are available from the profile measured at three different orientations. Janik, T. 2010. 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. Acta Geophysica 58: 543–586. Luosto, U., T. Tiira, H. Korhonen, I. Azbel, V. Burmin, A. Buyanov, I. Kosminskaya, V. Ionkis, and N. Sharov, 1990. Crust and upper mantle structure along the DSS Baltic profile in SE Finland. Geophysical Journal International 101: 89–110.

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