The FENNIA deep seismic sounding survey was carried out in the May of 1994 in Southern Finland (FENNIA Working Group 1998). The 330 km long profile is oriented from south to north and runs through the Svecofennian lithological units of the late orogenic migmatite, metasedimentary and metavolcanic belts of Southern Finland and the synorogenic Central Finland Granitoid Complex. Seismic refraction measurements were made by recording large explosions from six shot points with spacings of 60 to 80 km. 50 three-component seismic stations were deployed in three separate groupings during the experiment, equaling to 150 different station positions. Trial-and-error ray tracing method was used to obtain a two-dimensional crustal P-wave velocity model in 1998. The model shows thick crust (57 to 61 km Moho depth) in northern and central parts followed by an abrupt thinning of the crust to 48 km depth at the southern end of the profile. The seismic data was reprocessed in 2007 to address the inconsistencies in Moho depth data acquired by wide-angle, receiver function and reflection data. This yielded new two-dimensional P- and S-wave velocity models for the FENNIA profile obtained by similar ray tracing methods. The three available velocity models of the FENNIA profile were modeled by FENNIA Working Group (1998) and Janik et al. (2007). Wide-angle sections of three different seismic measurement axes are available for the FENNIA profile. FENNIA Working Group, 1998. P- and S-velocity structure of the Baltic Shield beneath the FENNIA profile in southern Finland. University of Helsinki, Institute of Seismology, Report S-38. Janik, T., E. Kozlovskaya, and J. Yliniemi, 2007. Crust-mantle boundary in the central Fennoscandian shield: Constraints from wide-angle P and S wave velocity models and new results of reflection profiling in Finland. Journal of Geophysical Research: Solid Earth 112.

2022