Geophysical research: article

Аnnotation: 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.