ONCE AGAIN ON THE ORIGIN OF SEISMICITY IN FENNOSCANDIA

A.A. Lukk*, V.G. Leonova, A.Ya. Sidorin

Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia

* e-mail: lukk@ifz.ru

Abstract. The vast body of literature concerning tectonics, seismicity and post- or endglacial faulting in Fennoscandia (Baltic Shield) has been reviewed. On this basis various concepts of the origin of current seismicity within the area under consideration have been appraised. A conclusion was derived that at least four different processes are responsible for the current seismicity: 1) the movement of the lithospheric plate under the Norwegian and Barents seas from the northwest to the southeast, as a result of the spreading of the Mid-Atlantic Ridge in the area from Iceland to Spitsbergen; 2) post-glacial isostatic uplift; 3) local recent neotectonic movements; 4) gravitational bending deformations on the contact of the continent and the sea shelf along the coast of Norway due to intense erosion from the rising crystalline domain of the Baltic Shield. The current seismicity of Fennoscandia is relatively low. The strongest earthquake within this area known for last about a thousand years was of magnitude of ≈ 6.5 and occurred in 1627 in the Kandalaksha graben in the White Sea. Nevertheless, in Fennoscandia, including the Kola Peninsula and Karelia in its eastern part, a significant number of Pleistocene and even Holocene seismic dislocations was reliably established, the parameters of which allow them to be associated with the occurrence of strong earthquakes with magnitudes of 7–8 and even more. Such paleo-events, most likely, occurred at the last stage of the glacial epoch (9–10 thousand years ago) during the intensive postglacial isostatic uplift of the Fennoscandia domain. Their possible recurrence can be estimated as tens of thousands of years based on the time interval between consecutive glaciations. Thus, it should be concluded that the origin of current seismicity of Fennoscandia is related not to postglacial, but to tectonic stresses, caused both by the global effect of the north-west uplifting lithospheric plate under the Norwegian Sea (constant source of tectonic stress accumulation) and by local tectonic uplifts (north coast of Norway), or lowering (the Swedish coast of the Gulf of Bothnia). In addition, the increased seismicity of the southwestern part of Norway and the adjacent North Sea shelf is most likely caused by the formation of graben-like structures under the influence of tensile stresses revealed here.

Keywords: Fennoscandia, current seismicity, postglacial seismicity, paleo-earthquakes, tectonics.

About the authors

LUKK Albert A. – Cand. Sci. (Phys. and Math.), leading researcher, Schmidt Institute of Physics of the Earth, Russian Academy of Sciences. Moscow, Russia. Tel.: +7 (499) 254-90-35. E-mail: lukk@ifz.ru

LEONOVA Vera G. – scientific researcher, Schmidt Institute of Physics of the Earth, Russian
Academy of Sciences. Moscow, Russia. Tel.: +7 (499) 254-90-35. E-mail: lukk@ifz.ru

SIDORIN Alexander Ya. – Cand. Sci. (Phys. and Math.), head of laboratory, Schmidt Institute
of Physics of the Earth, Russian Academy of Sciences.  Moscow, Russia. Tel.: +7 (499) 254-42-68. E-mail: al_sidorin@hotmail.com

Cite this article as: Lukk A.A., Leonova V.G., Sidorin A.Ya. Once again on the origin of seismicity in Fennoscandia, Geofizicheskie Protsessy i Biosfera (Geophysical Processes and Biosphere), 2019, vol. 18, no. 1, pp. 74–90 (in Russian). https://doi.org/10.21455/gpb2019.1-7

English version: Izvestiya, Atmospheric and Oceanic Physics, 2019, vol. 55, iss. 7. ISSN: 0001-4338 (Print), 1555-628X (Online). URL: https://link.springer.com/journal/volumesAndIssues/11485