Abstract
This paper is dedicated to the topical problem of examining permafrost’s state and the processes of its geocryological changes by means of geophysical methods. To monitor the cryolithozone, we proposed and scientifically substantiated a new technique of pulsed electromagnetic cross-well sounding. Based on the vector finite-element method, we created a mathematical model of the cross-well sounding process with a pulsed source in a three-dimensional spatially heterogeneous medium. A high-performance parallel computing algorithm was developed and verified. Through realistic geoelectric models of permafrost with a talik under a highway, constructed following the results of electrotomography field data interpretation, we numerically simulated the pulsed sounding on the computing resources of the Siberian Supercomputer Center of SB RAS. The simulation results suggest the proposed system of pulsed electromagnetic cross-well monitoring to be characterized by a high sensitivity to the presence and dimensions of the talik. The devised approach can be oriented to addressing a wide range of issues related to monitoring permafrost rocks under civil and industrial facilities, buildings, and constructions.
Highlights
The study of the state of permafrost, which occupies at least 25% of the world’s land area [1], is becoming an increasingly urgent scientific problem
The electromotive force (EMF) in the reference model has the simplest form: Its transition through zero is evidenced only at a depth of 15 m at late times. As for both talik-containing models, the corresponding EMFs differ from the mentioned one significantly: Zero crossing is manifested on all the graphs
The EMF in the reference model has the simplest form: Its transition through zero Geosciences 2021, 11, x FOR PEER REiVsIEeWvidenced only at a depth of 15 m at late times. As for both talik-containing m1o2doefls1,5 the corresponding EMFs differ from the mentioned one significantly: Zero crossing is manifested on all the graphs
Summary
The study of the state of permafrost, which occupies at least 25% of the world’s land area [1], is becoming an increasingly urgent scientific problem. This is owing to, first of all, climatic changes in recent decades, accompanied by an increase in the average annual air temperature on the Earth. To obtain a mathematical model describing the sounding process with a pulsed source of electromagnetic field excitation in a three-dimensional region with a complex physical and geometric structure, we use the Maxwell system of equations. Since the electromagnetic field source will be excited by a current pulse, the initial values of the fields are taken to be zero.
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