GEOPHYSICAL RESEARCH, 2019, vol. 20, no. 3, pp. 71-86. https://doi.org/10.21455/gr2019.3-5

UDC 550.348.436; 551.24

Abstract  References   Full text (in Russian)

THE SPECTRAL COMPOSITION OF MICROSEISMIC OSCILLATIONS AND SIZES OF ACTIVE STRUCTURAL-TECTONIC BLOCKS OF ROCKS AT THE SITE KURKIEKI (NORTH LADOGA AREA)

V.G. Spungin(1), V.A. Shekov(2), A.A. Ivanov(2), A.A. Lebedev(2)

(1) Institute of Geosphere Dynamics, Russian Academy of Sciences, Moscow, Russia

 (2) Institute of Geology Karelian Research Centre of the Russian Academy of Sciences, Petrozavodsk, Russia

Abstract. Observations of microseismic oscillations on the outcrops of the rock mass composed by Paleoproterozoic gneisses were carried out in order to study the structure and stress state of the rock mass, in particular, to determine the size of the structural-tectonic blocks of rocks currently exposed to minimal lateral stresses. The results of spectral analysis of micro-oscillations are used to determine the size of the currently active blocks by the frequency of spectrum anomalies. It seems that the most active, mobile at the present stage of geological history, blocks are also the most unloaded from external stresses.

The identity of the spectrum of background microoscillations in different parts of the studied array is established, which indicates the similarity of the sizes of active structural-tectonic blocks within its limits and the homogeneity of its block structure. The size of the active blocks composing the investigated area is determined by the frequency of spectrum anomalies. The size of the block, which is characterized by the greatest modern activity and, accordingly, less constraint compared to others, is determined.

Comparison of the spectral composition of microoscillations in the study area with the spectrum of micro-oscillations in two other areas, composed of rocks similar in composition but located in the zone of active regional faults, showed that in the fault zone the current activity (mobility) of structural-tectonic blocks is three and more times higher than in the study area. It is assumed that the higher mobility of the blocks in the fault zones is due to the decompaction of the medium in the band of their dynamic influence.

Keywords: rock mass, anomalies of the microseismic oscillations spectrum, mobility of structural-tectonic blocks.

References

Adushkin V.V., Spivak A.A., Spungin V.G., Diagnostics of the mechanical state of local areas of the earth's crust based on the study of relaxation processes, Geoecologiya (Geoecology), 1997, no. 4, pp. 45-52.

Gordeev E.I and Chebrov V.N., The use of storm microseisms to study the crustal topography, Vulkanologiya i seismilogiya (Vulcanology and seismology), 1979, no. 2, pp. 37-42.

Kapustyan N.K., Technogenic impact on the lithosphere – the object of planetary research of the XXI century, in Problemy geofiziki XXI veka (Problems of geophysics of the 21st century), Moscow: Nauka, 2003, pp. 213-244.

Khazov R.A., Sharov N.V., Isanina E.V. Deep structure and metallogeny of the Ladoga area, Geologiya i poleznye iskopaemye Karelii (Geology and useful minerals of Karelia), Petrozavodsk: KarNC RAN, 2004, no. 7, pp. 55-74.

Koroleva T.Yu., Yanovkskaya T.B., Patrusheva S.S., Implication of seismic noise for determing the structure of the upper Earth Rock Mass, Izv. Phys. Solid Earth, 2009, vol. 45, no. 5, pp. 369-380.

Kocharyan G.G. and Spivak A.A., Dinamika deformirovaniya blochnyh massivov gornyh porod (Dynamics of deformation of block massifs of rocks), Moscow: IKC “Akademkniga”, 2003.

Koshkin N.I., Shirkevich M.G., Spravochnik po elementarnoi fizike (Handbook of Elementary Physics), Moscow: Nauka, 1972.