The results of detailed paleoseismological
studies in the Kindo Peninsula area
(Karelian coast of the White Sea)

 

E.S. Gorbatov¹, A.A. Sorokin^{1, 2}, A.V. Marakhanov¹, A.S. Larkov¹

 

¹Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia

 

²Moscow State University of Geodesy and Cartography, (MIIGAiK), Moscow, Russia

 

Corresponding author: E.S. Gorbatov, e-mail: e.s.gor@mail.ru

 

Abstract. In order to identify, parameterize and date the seismic dislocations of the Karelian coast of the White Sea, a standard set of geomorphological methods was used, including the interpretation of aerial and satellite imagery, topographic and structural geomorphological surveying on the ground, trenching through colluvial accumulation and their documentation, sampling of buried paleosoil and their dating by the radiocarbon method. In addition, a set of kinematic indicators of paleoearthquakes (mass displacements and systematic reversals of fragments of rocky ledges) has been developed and tested. It allowed us to reconstruct the directions of the maximum seismic effect in detailed areas. Using these methods, we revealed in the relief of rock massifs in the Kindo Peninsula region the area (10×6 km) of secondary seismic dislocations with the radiocarbon age not more than 5.5 thousand years. The area is a zone (4×2 km) of the development of tension cracks, numerous dislocations, and rock blocks, surrounded by a belt of earthquake-induced disturbances. It is shown that individual ledges and stepwise disturbances in the relief of rock massifs are apparently the result of glacial denudation and subsequent erosion of structural heterogeneities. At the same time, the displacement of the punctured blocks against the slope and their systematic turns in the rock ledges of various prostrations suggest intense seismic effects even after the formation of the stepped surfaces and the completion of their abrasion treatment during the post-glacial elevation of the territory. It has been established that the effects of high-frequency seismic oscillations with high values of peak accelerations (0.4–0.8g) and velocities (100–300 cm/s) are necessary to form block displacements. To determine the location of the paleoearthquake epicenter, the directions of the maximum seismic effect were reconstructed at several points with the kinematic indicators. Possible zones of shocks with intensity 7 and 8 are examined in order to assess the depth of the focus (H = 1.9±0.2 km) and magnitude (M = 4.4±0.2) of the seismic event according to the macroseismic field equation. The characteristic elongation of the first isoseist along the northern coast of the Kindo Peninsula toward the WNW shows that the seismic events were caused by he rupture of the southern restriction of the micrograbene Great Salma Strait, feathering the south-eastern side of the Kandalaksha graben. The Holocene activity of this rupture is confirmed by the normal fault displacement of recent sediments, revealed on a series of transverse seismoacoustic profiles. The results obtained for the first time at a quantitative level showed that low-magnitude shallow earthquakes with high seismic intensity could occur in the Kandalaksha graben zone in the Holocene.

 

Keywords: displacement of rock blocks, kinematic indicators, secondary paleoseismodislocations, glacial denudation, Kandalaksha neotectonic graben, White Sea.

 

 

About the authors

 

GORBATOV Evgeny Sergeevich — Candidate of Geological and Mineralogical Sciences, Senior Researcher, Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences. 123242, Moscow, ul. Bolshaya Gruzinskaya 10, stroenie 1. Tel.: +7 (499) 254-99-50. E-mail: e.s.gor@mail.ru

 

SOROKIN Andrey Andreevich — Leading Engineer, Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences. 123242, Moscow, ul. Bolshaya Gruzinskaya 10, stroenie 1. Tel.: +7 (499) 254-99-50; Master of the Department of Cartography of the Moscow State University of Geodesy and Cartography (MIIGAiK). 105064, Moscow, Gorokhovskii per. 4. Tel .: +7 (499) 322-78-00. E-mail: aas@ifz.ru

 

MARAKHANOV Alexander Vladimirovich — Senior Researcher, Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences. 123242, Moscow, ul. Bolshaya Gruzinskaya 10, stroenie 1. Tel.: +7 (499) 254-90-15. E-mail: marahanov@ifz.ru

 

LARKOV Alexander Sergeevich — Research Fellow, Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences. 123242, Moscow, ul. Bolshaya Gruzinskaya 10, stroenie 1. Tel.: +7 (499) 254-92-15. E-mail: las119@yandex.ru

 

Cite this article as: Gorbatov E.S., Sorokin A.A., Marakhanov A.V., Larkov A.S. The results of detailed palaeoseismological studies in the Kindo Peninsula area (Karelian coast of the White Sea), Voprosy Inzhenernoi Seismologii (Problems of Engineering Seismology), 2017, Vol. 44, No. 3, pp. 5–24. DOI: 10.21455/VIS2017.3-1 [in Russian].

 

English translation of the article will be published in Seismic Instruments, ISSN: 0747-9239 (Print) 1934-7871 (Online), https://link.springer.com/journal/11990), 2018, Volume 54, Issue 3.