Science and technological developments: article

1 Lomonosov Moscow State University 2 Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences
Journal: Science and technological developments
Tome: 99
Number: 1
Year: 2020
Pages: 31-58
UDK: 550.837.311
DOI: 10.21455/std2020.1-4
Аnnotation file
Bibliographic list
Keywords: vertical electrical sounding, precision monitoring, data inversion, instability features of the inverse problem solution
Аnnotation: When solving many geophysical problems, monitoring by the method of vertical electrical sounding (VES) is used on stationary multi-electrode installations. The resulting time series of observations can be considered as a profile (set of pickets) of the VES, deployed not in space, as with profile soundings, but in time. When solving the VES inverse problem for precision monitoring data on a stationary multi-electrode VES array, the effect of a high-amplitude antiphase change in the resistivity of adjacent layers in time was discovered. This behavior is physically unlikely. To clarify the causes of this phenomenon, synthetic VES profiles, similar to real ones, were studied. In each layer of the model section, the law of change in time (along the profile) of the resistivity was set and synthetic curves of apparent resistivity were calculated. Then the inverse problem of VES was solved. In this case, the same algorithms were used that were used for the experimental series. The obtained solutions were compared with the original synthetic resistivity profiles, which made it possible to analyze the solution errors. The results of the analysis showed that the effect of the antiphase change in the resistivity of the adjacent layers of the section (the swing effect of the solution to the inverse problem) is not associated with real changes in the resistivity. It arises due to the special structure of the landscape of the discrepancy due to the equivalence in resistance. This feature is not taken into account by standard algorithms for solving the inverse problem and can lead to rather large errors if no special countermeasures are taken. When monitoring a geoelectric section, increased requirements are imposed on the accuracy of solving the inverse problem of VES. The required accuracy cannot be achieved with commonly used inversion algorithms. It is required to develop special algorithms for selecting a solution to the inverse problem, which provide suppression of the swing.