The Geoelectromagnetic Research Institute was founded in 1993 and is presently one of the Institutions forming the United Institute of the Physics of the Earth (UIPE). GEMRI employs now 55 staff, of whom the 35 are R&D employees (including 5 Professors).

The main directions of scientific activity of GEMRI are as follows:

- theory of electromagnetic fields (EM) of natural origin taking into accout anisotropy and frequency dispersion of the conductivity;

- physical and mathematical foundations of interrelation of seismic and electromagnetic phenomena in porous and watersaturated rocks;

- advanced algorithms and software packages for numerical modeling of EM fields in 2D/3D anisotropic media induced in the earth by natural and controlled sources;

- methods for 2D/3D inversion of EM data based on using conjugate gradients, Bayseian statistics and artificial neural network techniques;

- high resolution near-surface time domain electromagnetics;

- marine electromagnetics;

- regional MT studies aimed at construction of 3D conductivity models (Juan de Fuca subduction zone, Caucasus, Tasmania Island, Minou fracture zone, etc.);

- application of EM methods to environmental investigations;

- magnetotelluric monitoring in geodynamic areas (in particular, at Tjan Shan testing site);

- electromagnetic instrumentation for high-resolution TDEM surveys.

A number of international Projects (in particular, EUROPROB, BEAR, etc.) funded by EC, OYO Co. (Japan), Russian Basic Research Foundation as well as by national science foundations of the countries involved were fulfilled by GEMRI in cooperation with scientists from the Universities of Paris, Napoli, Edinburg, Kyushu, Cair, Hobart, etc.

GEMRI has initiated and presently leads some International Projects aimed at comparison of numerical codes for processing EM data (COMDAT), 3D modeling (COMMEMI), 2D inversion (COPROD - 2S).

Scientists of GEMRI gave lectures and seminars on theory and methods of numerical modeling and inversion of EM fields at the Universities and Institutions of Montreal, Roma, Napoli, Paris, Hobart, Colorado School of Mines, Geological Surveys of Canada and Japan, Ettore Majorana Foundation and Centre for Scientific Culture (Erice), etc.

(Divisions I, II and V of IAGA)

GEMRI conducted research in the following lines:

1. Development of universal method of solution of Maxwell equations in inhomogeneous conductive medium (named modified Iterative Dissipative Method - IDM), which is widely applied in numerical modeling of EM fields induced in the earth by sources of arbitrary origin.

2. The general nonlinear inversion approach, developed within the class of fixed-geometry 2D structures is extended for the case of piece-wise continuous conducting media in 2D and full 3D formulations (Golubev, Varentsov, 1997; Varentsov, 1998). Several schemes to approximate conductivity within scanning “windows” are elaborated, like parametrization with independent or pseudo-correlated cell resistivities or schemes based on Strakhov's "finite" functions.

3. Elaboration of the Artificial Neural Network Expert System for recognition of 3D inhomogeneities burried in a layered earth by noisy and incomplete MT data.

4. Development of the method for 3D inversion of EM data in inhomogeneous media taking into account the apriori information and formalized geophycisist’s experience.

5. Development of physical and mathematical background of seismoelectrical transformations in porous watersaturated media (rocks). It enables to understand the nature of low - frequency electromagnetic fields, connected with geodynamic and other mechanical processes inside the earth.

6. The informational-statistical model of electromagnetic field of the ocean is developed on the basis of information theory and thermodynamics. The model intends for solution of three problems: (1) interpretation of probabilistis distribution of the field, (2) determination of dependence measure of its elements and causal interpretation and (3) computation of the field on the aquatory in real time by observation at a reference site.

7. Development of techniques aimed at fast 3D imaging of geoelectrical structures basing on EM data measured at a relief earth surface or in the atmosphere.

1. A number of 3D modelling schemes based on IDM taking into account the displacement currents and electrical anisotropy of the formation are developed and applied to a wide range of geophysical applications: tectonomagnetics, magnetotellurics, grounded controlled-source electromagnetics, airborne electromagnetics, induction logging, global induction studies and water-motion induction studies.

2. An intensive mathematical modeling of the natural as well as controlled-source EM fields in a layered media with a frequency dispersion is carried out. It is determined that the resolution of the electromagnetic sounding in such a media increases.

3. Verification of computer software used in MT data analysis and other EM induction studies, i.e. the development of proper tests (including construction of special synthetic data sets) and organization of cooperative efforts to study existing algorithms and codes in frames of the international comparative projects of the IAGA WG I.2. The first COMMEMI project of this type aimed at testing modeling tools is already completed (Zhdanov et al., 1997). Recently two new projects based on synthetic data sets designed in GEMRI were launched: the COMDAT project to test MT data processing tools (Sokolova, Varentsov, 1998) and the COPROD-2S project to study 2D MT inversion tools (Varentsov, 1998).

1. Construction of 3D conductivity models basing on synthetic and real MT data (Juan de Fuca subduction zone (EMSLAB experiment), Kilauea volcano, Caucasus, Tasmania Island, Minou fracture zone, Minami-Kayabe geothermal reservoir, etc.).

2. Re-interpretation of the EMSLAB project MT soundings at the Lincoln line profile was held with a special care for the resolution of inhomogeneous conducting asthenosphere (Varentsov et al., 1996). This research based on the use of new bi-modal 2D inversion schemes and the application of original schemes to control static shift distortions by GDS data transforms (Vanyan et al., 1997) gave a new understanding of the upper mantle conductivity structure of the area. An integral equation technique to extract simultaneous magnetic component data from profile arrays of single site induction vector estimates was specially designed and succesfully tested in this study (Vanyan et al., 1998).

3. Investigation of the nature of conductive layers in the crust of ancient platforms at the depth 10-12 km. It is shown that increased conductance is caused by specific P-T conditions, amphibolite minerals and by water penetration inside and through faults and cracks.

4. Development of new technology (TEM-FAST), instrumentation and software for application of TDEM in environmental investigations.

5. Collection of a large volume of MT monitoring data at one of seismo-active regions of Tjan-Shan (6 years, discretization -10s) . It is found that the dynamics of the appropriate transfer functions is in some extent connected with alterations of the energy of the geodynamical processes studied.

6. Data processing and interpretation in the Baltic Electromagnetic Array Research (BEAR) Project. The BEAR project, an integral part of an international, multidisciplinary EUROPROBE SVEKALAPKO project, realizes an ultra deep EM sounding using a shield wide magnetotelluric and magnetometer array. Almost 50 portable MT instruments and 20 additional magnetic stations run simultaneously for 2 months during the summer 1998. Now the standard MT and GDS processing stage is almost completed. Robust processing codes (Varentsov et al., 1997) will be used to produce stable transfer functions (single station and remote reference) for periods from 10 sec till 6-12-24 hours with minor polar inhomogeneous source distortions (Varentsov et al., 1999) for sites even at the polar circle.

7. A long-term geophysical experement on verification of the hypothesis on non-local interaction of the dissipative processes is carried out. The experimental setup inlculed a detector of the non-local interaction based on measuring of self-potentials of the marine electrodes protected from the known source effects. Number of new effects is discovered: correlation of the potentials on the distant setups, advanced reaction of the potentials on the geomagnetic variations, sudden ionosphric disturbances and solar activity. The results agree with predictions of the hypothesis, combining the ideas of causal mechanics, quantum non-locality in a strong macroscopic limit and action-at-a-distance electrodynamics. The advanced time Pag of the nonlocal interaction allows to develop a principle new method of geophysical forecast.