Methods of geophysics engineering in the search for technogenic structures in shallow waters

Abstract

Introduction: In the present work we studied the problem of the identification of technogenic structures in shallow waters which were concealed due to the process of sedimentation. To solve the task, we suggested a complex approach based on the results of the interpretation of the conducted measurements of the modulus of the magnetic induction vector in accordance with the proposed survey method supported by seismoacoustics methods. Methodology: Unwieldy equipment and large water vessels cannot be used in shallow waters or in an area limited by coastlines. Thus, it was suggested to develop a set of methods and a working methodology involving the use of small water vessels during the search and discovery of unpredictable discrete magnetised structures. Based on the previous studies involving extensive linear technogenic structures, we used hydroacoustic, magnetometric, and geoacoustic methods in a step-by-step manner. Methodological provision of each type of the conducted work includes solvability which guarantees the identification of the goals and sufficiency of the collected information providing a general understanding of the condition of the water area. Results and discussion: A hydroacoustic survey, as a visualisation tool, allowed studying the degree of the bottom’s cluttering with anthropogenic structures, although it could not unambiguously identify the fragments of the tank, as over a long period of time it had been all levelled with the stream sediment. Two significant anomalies of the magnetic field were found as a result of the conducted magnetometric observations. A quantitative interpretation of magnetic anomalies was conducted for a two-dimensional case: a conversion to the upper half area was performed, and an estimate of the depth of the structures was presented. As a result of the conducted work using the geoacoustic method, the depths of the river’s water area were specified. The overall results of the used set of methods allowed solving the direct problem of magnetometry using Mathcad 14. As a result of the modelling performed in Mathcad 14, the calculated field of the modulus of the induction vector from the set of model sources showed good correlation with the observed field. Direct diving surveys which were performed after the completion of the survey stage confirmed the presence of the body of the tank and tank tower covered with river sediments. Conclusions: The main results of our research aimed at ensuring the safety of economic activities in shallow water areas while searching for unpredictable magnetised technogenic structures are the improvement of the hydromagnetic survey method with the further interpretation of data, including computer modelling, as well as the development of an optimal complex of geophysical works.