Baikal Electromagnetic Experiment

Izvestiya, Atmospheric and Oceanic Physics - The vertical component of the electric field Ez in the hydrosphere is not contaminated by the telluric component and therefore can effectively be used...     

Study of the possibility of the use of the magnetotelluric sounding method in the Arctic ocean with quantitative modeling

The task of the magnetotelluric (MT) sounding of the heterogeneous deep section of the Arctic ocean floor on the idealized model of gorst and graben lying on the typical oceanic, or continental Earth’s, crust is solved with the use of 3D quantitative modeling. In both cases, the sequence is covered by a layer of seawater with a thickness of 4 km. In this work, the difference in the MT sounding with the use of ocean-floor and surface equipment is considered. As a result, the conclusion was made that the floor equipment has a higher resolution than the surface equipment, in spite of the fact that the observations from the ice cover’s surface can be done more easily.     

High-Performance Parallel Solver for Integral Equations of Electromagnetics Based on Galerkin Method

A new parallel solver for the volumetric integral equations (IE) of electrodynamics is presented. The solver is based on the Galerkin method, which ensures convergent numerical solution. The main features include: (i) memory usage eight times lower compared with analogous IE-based algorithms, without additional restrictions on the background media; (ii) accurate and stable method to compute matrix coefficients corresponding to the IE; and (iii) high degree of parallelism. The solver’s computational efficiency is demonstrated on a problem of magnetotelluric sounding of media with large conductivity contrast, revealing good agreement with results obtained using the second-order finite-element method. Due to the effective approach to parallelization and distributed data storage, the program exhibits perfect scalability on different hardware platforms.     

Electromagnetic sounding of the Kola Peninsula with a powerful extremely low frequency source

Experiment on electromagnetic sounding of the Kola Peninsula using unique mobile measuring complex of the low-frequency sounding was conducted, allowing to investigate a geoelectric section with a depth of several kilometers on distances up to 100 km from the stationary transmitting aerial. Excess on the order of amplitudes of the vertical component above the horizontal at all frequencies of sounding was registered in a number of points of measurements. This feature managed to be explained quantitatively by circulation of current on regional faults with the closure of current through the sea—before unknown galvanic coastal effect. Interpretation of the results of modeling and neural network solving of inverse problem essentially specifies the fault tectonics of the central part of the Kola Peninsula. Anomaly remote from the observation profile was found out—local pinch of a crustal conductive layer consisting of graphitized rocks and associated with the zone of overthrust.     

Prospects of magnetotelluric sounding in some large structures in the Arctic ocean

In the work, the results of modeling of electric resistivity distribution at the Gakkel and Alpha-Mendeleev underwater ridges are given. Based on the seismostratigraphic models, the apparent resistivity curves at a few points of the profile at the crossing of the ridge were constructed. The advantages and disad-vantages of the MT sounding method are presented. The results obtained can be used for future experiments.     

The results of marine electromagnetic sounding with a high-power remote source in the Kola Bay in the Barents Sea

The first Russian six-component seafloor electromagnetic (EM) receivers were tested in an experiment carried out in Kola Bay in the Barents Sea. The signals transmitted by a remote high-power ELF source at several frequencies in the decahertz range were recorded by six receivers deployed on the seafloor along the profile crossing the Kola Bay. Although not all the stations successfully recorded all the six components due to technical failures, the quality of the data overall is quite suitable for interpretation. The interpretation was carried out by the three-dimensional (3D) modeling of an electromagnetic field with neural network inversion. The a priori geoelectrical model of Kola Bay, which was reconstructed by generalizing the previous geological and geophysical data, including the data of the ground magnetotelluric sounding and magnetovariational profiling, provided the EM fields that are far from those measured in the experiment. However, by a step-by-step modification of the initial model, we achieved quite a satisfactory fit. The resulting model provides the basis for introducing the corrections into the previous notions concerning the regional geological and geophysical structure of the region and particularly the features associated with fault tectonics.