Finland is located on the Fennoscandian Shield that consists of old and stable bedrock. The thickness of the crust in Finland is up to 65 km which is thicker that typically on a continental shield (about 42 km). Exceptions are for example the Himalayas and Andes where the thickness of the crust is up to 80 km.
The lithosphere, i.e., the crust and the upper parts of the mantle beneath, can be effectively studied using seismic waves that propagate through the subsurface and reflect and refract from the interfaces (or internal boundaries) within the subsurface. These seismic soundings use for example explosions and vibrators trucks as sources. The seismic waves traveling through the subsurface are recorded on the surface using geophones (on land) or hydrophones (on water).
The structure of the lithosphere can also be studied using seismic tomography which uses seismic signals from mining and road construction explosions or even earthquakes to "x-ray" the earth's crust and mantle. Field work is usually done in international collaboration since it requires large resources (staff, hardware, diverse know-how).
The lithospheric structure of Finland has been extensively mapped over the years by seismic soundings, most recently by KOKKY (Kokkola-Kymenlaakso) and SOFIC (Southern Finland Coastal Profile) projects in 2012-2013 and 2015, respectively. The last major reflection sounding project in Finland was the FIRE (Finnish Reflection Experiment).
Institute of Seismology and its partners maintain the data listed below. For more details, please contact the director of the institute Timo Tiira (see Contact information).
Deep seismic refraction survey SOFIC was conducted in 2015 and it runs through southern Finland from Kemiö Island to Ylämaa. It covers the late Svecofennian granite-migmatite belt to Vyborg batholith.
Publications
KOKKY refraction line runs through the Central Finland granitoid complex to Vyborg batholith. It was conducted in 2012 and 2013 using passive sources (i.e., using seismic signals generated by quarries and road constructions sites).
Tiira, T., Skrzynik, T., Janik, T., Komminaho, K., Väkevä, S., and Korja, A. (2017). Lithospheric studies along seismic profile KOKKY, between Gulf of Bothnia and Gulf of Finland, Baltic Shield. Geophysical Research Abstracts, vol. 19, EGU2017-7817.
The aim of the POLENET/LAPNET project was to carry out a temporary broadband seismic array research in the northern Fennoscandia in order to study the deep structure of the crust and upper mantle and the anisotropy of the upper mantle. The array consisted of temporary stations and permanent broadband stations operated by Oulu University, Institute of Seismology of Helsinki University, Swedish National Seismological Network, Bergen University and NORSAR.
The data can be downloaded from RESIF-SISMOB data bank under name XK.
The Finnish Reflection Experiment (FIRE) dataset consists of seismic reflection data from 2,104 km. The project took place between 2001 and 2005. It was conducted in co-operation between the Geological Survey of Finland (GTK), the Institute of Seismology at the University of Helsinki and the Institute of Geosciences and the Sodankylä Geophysical Observatory of the University of Oulu. The seismic contractor in the FIRE project was Specgeofizika S.E. together with Machinoexport S.E.
The FIRE data are hosted at CSC - IT Center for Science Ltd. Links to datasets can be found at the FIRE webpages.
Heinonen, A., Aalto, A. J., Väkevä, S., Heikkinen, P. J. and Korja, A. (2017). OpenFIRE – Suomen syvyydet avataan verkkoon. Geologi, issue 69(3), p. 92-97.
Väkevä, S., Aalto, A.J., Heikkinen, P.J., Heinonen, A. and Korja, A. (2017). OpenFIRE – A Web GIS Service for Distributing the Finnish Reflection Experiment Datasets. Geophysical Research Abstracts vsk 19, EGU2017-7099, 2017, EGU General Assembly 2017.
Aalto, A. J., Heikkinen, P. J., Heinonen, A., Korja, A. and Väkevä, S. (2016). OpenFIRE – enhancing the accessibility of the Finnish Reflection Experiment data products. Lithosphere 2016, Programme and extended abstracts, 9.–11.11.2016, Institute of Seismology, p. 1-4.
Kukkonen, I.T., and Lahtinen, R. (eds., 2006): Finnish Reflection Experiment FIRE 2001–2005. Geological Survey of Finland, Special Paper 43, 247 p.
In the autumn of 2000, a geophysical survey was carried out in the northern Baltic Sea, involving a shallow seismic sounding (0–3 km) and gravimetric and magnetic observations from 16 lines with a total length of about 1,300 km. The survey was done in international collaboration of Universities of Hamburg, Helsinki and Tartu. The purpose of the survey was to collect data on the geological-geophysical structure of the Baltic Sea and in particular on the sedimentary basin of the Baltic Sea, Northern Baltic Sea rapakivigranite area and Åland-Paldinski-Pskov shear zone. Theses by Minna Kuusisto (2003) and Kati Karkkulainen (2008) used the CRUISE2000 data. The research was funded by Väisälä Foundation.
Kuusisto, M., (2003). Pohjoisen Itämeren seisminen heijastusluotaus: Ahvenanmeren aineiston prosessointi ja tulokset. MSc thesis, Department of Physics, University of Helsinki, 66 p. 5 appendices.
Kuusisto, M., Heikkinen, P. and Korja, A., (2002). A Geophysical Study of the Northern Baltic Sea. In: Lahtinen, R., Korja, A., Arhe, K., Eklund, O., Hjelt, S.-E., and Pesonen, L.J. (Eds.). Lithosphere 2002 – Second Symposium on the Structure, Composition and Evolution of the Lithosphere in Finland. Programme and Extended Abstracts, Espoo, Finland, November 12–13, 2002. Institute of Seismology, University of Helsinki, Report S-42, p. 71-74.
EUROPROBE/SVEKALAPKO project carried out large scale tomographic survey where an array of 85 temporary short period stations and 39 broadband stations were installed to measure in Southern and Central Finland. In addition, the project used 14 permanent seismic stations.
Data are available via CSC - IT Center for Science Ltd. here.
FENNIA line was conducted in 1994 and it runs in S-N direction from Uusimaa region through Häme and Tampere belts to Central Finland granitoid complex. FENNIA line runs parallel to FIRE2 reflection seismic line.
Several theses have been completed using the FENNIA data.
FENNIA data are available via CSC - IT Center for Science Ltd. here.
FENNIA Working Group (1998): P- and S-velocity structure of the Fennoscandian shield beneath the FENNIA profile in southern Finland. Institute of Seismology, University of Helsinki. Report S-38, 15 p.
BABEL marine seismic reflection soundings were carried out in 1989. Some of the receiver stations were located on land. The data is of excellent quality and therefore, it has resulted in several international peer-reviewed publications. The data and interpretations of the data are available through Virtual Seismic Atlas services. Data are also available from CSC - IT Center for Science Ltd. here.
Buntin, S., Malehmir, A., Malinowski, M., Högdahl, K., Juhlin, C., Thybo, H., and Buske, S. (2016). Seismic reprocessing of the BABEL lines for improved interpretation of the whole crust – preliminary result. In: Kukkonen, I.T., Heinonen, S., Oinonen, K., Arhe, K., Eklund, O., Karell, F., Kozlovskaya, E., Luttinen, A., Lahtinen, R., Lunkka, J., Nykänen, V., Poutanen, M. and Tiira, T. (Eds.). Lithosphere 2016 – Ninth Symposium on the Structure, Composition and Evolution of the Lithosphere in Finland. Programme and Extended Abstracts, Espoo, Finland, November 9–11, 2016. Institute of Seismology, University of Helsinki, Report S-65, p. 9-12.
POLAR refraction soundings were conducted in 1985 as an international cooperation. The line is the northernmost part of the European Geotransect (EGT) that runs from Mediterranean to the Arctic Ocean. The aim was to study the medisedimentary gneisses of the Lappland Granulite Belt and their transition to Archaean Inari terrain. FIRE4A line runs parallel to the POLAR line.
POLAR data and interpretation of the data has been published in several international peer-reviewed publications and theses. The data profiles and their interpretations are also published as separate posters in Tectonophysics special volume 162 in 1989.
POLAR data are hosted at CSC - IT Center for Science Ltd. and can be accessed here.
BALTIC refraction survey was conducted in 1982. It confirmed the thickness of the Finnish crust, first noted during the SVEKA81 survey. BALTIC line is part of the EU-3 geotransect that runs from Black Sea to Arctic Ocean.
Several international peer-reviewed articles and theses have been published using BALTIC data in Finland and beyond.
Data are hosted at CSC - IT Center for Science Ltd. and can be accessed here.
SVEKA seismic soundings were conducted in 1981 and 1991 as an international cooperation. The SVEKA81 was the first Finnish deep seismic sounding and as a result of the survey, it was noted that the crust is over 50 km deep in Finland. The continuation of SVEKA, SVEKA91 was carried out ten years later in August 1991.
FIRE1 follows the SVEKA81 line. The Global Geoscience Transect (GGT/SVEKA) used SVEKA lines as framework for the sounding.
SVEKA data are hosted at CSC - IT Center for Science Ltd, and can be accessed via following links:
Grad, M., and Luosto, U. (1987). Seismic Models of the Crust of the Baltic Shield along the Sveka Profile in Finland. Annales Geophysicae, vol. 5B, p. 639-650.
In 1965, the Institute of Seismology carried out a seismic refraction sounding project in the Gulf of Bothnia. The line runs from Pyhäranta to Sylen. The original data of the Porvoo/Sylen line has been lost.
Luosto, U. (1986). Reinterpretation of Sylen–Porvoo refraction data. Report S-13, Institute of Seismology, University of Helsinki.
Luosto, U. (1968). Refraction seismic study of the Earth's crust along the line Sylen–Porvoo. Publ. Inst. Seismology, Univ. Helsinki, 102, 39 p.
Luosto, U. (1967). Preliminary results of a seismic refraction study of the Earth's crust in S.W. Finland. Geophysica, vol. 9, p. 301–309.
The Finnish Reflection Experiment (FIRE) dataset consists of seismic reflection data from 2,104 km. The project took place between 2001 and 2005. It was conducted in co-operation between the Geological Survey of Finland (GTK), the Institute of Seismology at the University of Helsinki and the Institute of Geosciences and the Sodankylä Geophysical Observatory of the University of Oulu. The seismic contractor in the FIRE project was Specgeofizika S.E. together with Machinoexport S.E.
The FIRE data are hosted at CSC - IT Center for Science Ltd. Links to datasets can be found at the FIRE webpages (link below).
Moho (Mohorovičić discontinuity) is the boundary between the Earth's crust and the mantle.