TO THE PROBLEM OF ACCOUNTING PALEOEARTHQUAKES WHEN EVALUATING THE SEISMIC HAZARD OF FENNOSCANDIA

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

* e-mail: lukk@ifz.ru

Abstract. Earthquakes of magnitude M ≥ 6.5 are unknown in Fennoscandia for almost 900 years of historical data, but a sharp outburst of postglacial seismic activity with earthquake magnitude up to M ≥ 8 revealed by paleoseismogeological studies occurred there in 11 000–9000 years ago. This outburst sharply decreased in time to a relatively low modern seismic activity almost exponentially. The strong paleoearthquakes were not randomly distributed over time, but in the form of a group, or a cluster, confined to the maximum phase of deglaciation. It indicates a sharp non-stationary mode of paleoseismicity. On this basis, a conclusion was drawn on the fundamental difference between the geodynamic regimes of paleo- and ordinary modern seismicity. As a result of analysis of the historical seismicity of Fennoscandia over the past ~900 years, it was found that the magnitude of the strongest known earthquake, in contrast to paleo-earthquakes, did not exceed 6.5. It is logical to assume that the occurrence of earthquakes of intensity 9–10 on the territory of Fennoscandia is hardly possible at present and in the near future. Therefore, when assessing its seismic hazard and the environs of critical engineering facilities, including nuclear power plants, it is hardly necessary to take into account paleoearthquakes. An exception may be the assessment of seismic hazard for disposal sites of highly toxic and nuclear waste, the biological hazard period of which can reach 100 thousand years or more, which is comparable with periods of glaciation.

Keywords: Fennoscandia, deglaciation, paleoearthquakes, modern seismicity, seismic regime, seismic hazard assessment

About the authors

LUKK Albert A. – Cand. Sci. (Phys. and Math.), leading researcher, Schmidt Institute of Physics of the Earth, Russian Academy of Sciences. Russia, 123242, Moscow, Bolshaya Gruzinskaya st., 10-1. 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. Russia, 123242, Moscow, Bolshaya Gruzinskaya st., 10-1. Tel.: +7 (499) 254-42-68. E-mail: al_sidorin@hotmail.com

Cite this article as: Lukk A.A., Sidorin A.Ya. To the problem of accounting paleoearthquakes when evaluating the seismic hazard of Fennoscandia, Geofizicheskie Protsessy i Biosfera (Geophysical Processes and Biosphere), 2019, vol. 18, no. 4, pp. 129–145 (in Russian). https://doi.org/10.21455/gpb2019.4-11

English version: Izvestiya, Atmospheric and Oceanic Physics, 2019, vol. 55, iss. 11. ISSN: 0001-4338 (Print), 1555-628X (Online). https://link.springer.com/journal/volumesAndIssues/11485