Some features of fluid dynamics at platforms as illustrated by the example of variations in subsoil radon and seismic noises in the Moscow and Nizhni Novgorod regions

Abstract

Huge areas of ancient platforms are traditionally ascribed to geodynamically passive structures of the Earth’s crust. This leads to some conservatism in the interpretation of diverse natural phenomena at platforms (landslide, karst‐suffosional processes, rock impacts and gas explosions in mines, breakups of pipelines, and others), which are typically related to the exogenous change in the geological environment of the sedimentary cover [1]. However, following Kropotkin [2], who pointed to a possible relation of global change in the strain-deformational state of the Earth’s crust with variations in the Earth’s rotation, we demonstrated [3] that these processes affect fluid dynamics in both geosynclinal (seismically active) and platformal regions, thus defining the evolution dynamics of exogenous processes in decompressed areas of sedimentary cover that are formed above faults in the crystalline basement. The processes determine the rhythmic evolution of diverse geodynamic phenomena at platforms, including weak seismic activity [4]. Our previous research in seismically active regions showed that changes in the fluid dynamics of faults caused by variations in the strain-deformed state of the rocks is adequately correlated with variations in the radioactive and hydrocarbon emanation [5] and seismic noises [6]. Temporal series of the measured parameters of the aforementioned fields reflects the entire spectrum of variations in the strain-deformational state of the Earth’s crust, from secular (60 to 70 years) to circadian tidals (12 h and less). This allows one to use the emanation and seismic emission methods as highly sensitive noise-proof technologies for monitoring the geological environment, especially suitable for urban agglomerations, where the level of electromagnetic and vibrational‐noise emanation rules out or constrains the application of many methods of geophysical monitoring.