Anamolous modulations of electromagnetic field during increased seismic activity

Rautian T.G., Khalturin V.I., Fujita K., Mackey K.G., Kendall A.D.

The size of local and regional earthquakes in the former Soviet Union (USSR) has been given by the energy class ( K -class) system since the late 1950s. K -class was originally developed as a rapid and simple means of estimating the radiated energy ( E ) from an earthquake and was defined as K = log10 E (in joules). The nature, origin, and methodology of this system are poorly known to Western seismologists studying Soviet and Russian seismological data, and yet are of great interest and importance to those conducting detailed research on the seismicity of the former USSR. Since its inception, K -class has been the primary means of quantifying the size of small events in the former USSR and continues to be used for that purpose today. In most of this region, scientists employed the method of Rautian (1960), using the maximum horizontal (for the S wave) and vertical (for the P wave) amplitudes, which became the standard for local and regional networks in the early 1960s. In this paper, we describe the origins and basic principles of the energy class system, as well as the methodology generally used today by the regional networks (figure 1) of the states of the former USSR. Shortly after World War II, between 1946 and 1949, three large earthquakes occurred in Soviet Central Asia and triggered an intense study of seismicity. After the magnitude 7.4 Khait earthquake of 10 July 1949, the Geophysical Institute (now the Institute of Physics of the Earth) of the USSR dispatched an expedition to Garm, Tajikistan (figure 1), to deploy a temporary network around the epicentral region. This Complex Seismological Expedition (CSE), which included the senior authors of this paper (Khalturin and Rautian) at its inception, became permanent in 1954. The study of regional seismicity was not well-developed …

Bogomolov L., Bragin V., Fridman A., Makarov V., Sobolev G., Polyachenko E., Schelochkov G., Zeigarnik V., Zubovich A.

On the base of the GPS-measured velocity field referring to the recent crust movements over sizable terrestrial areas (Central Tien Shan), the strain rate tensor is evaluated as the tensor components are governed by space gradients of the velocity field. The areas of the extreme values of the strain rate tensor components are shown to coincide with the highest seismic activity areas. Also shown is the fact that, in the direction of the crust surface layer compression, the deep layer electric conductivity reaches its maximum. A simplest explanation of this phenomenon is proposed.

Nepeina K., Bataleva E., Alexandrov P.

This study focuses on microscale anisotropy in rock structure and texture, exploring its influence on the macro anisotropic electromagnetic parameters of the geological media, specifically electric conductivity (σ), relative permittivity (ε), and magnetic permeability (μ). The novelty of this research lies in the advancement of geophysical monitoring methods for calculating cross properties through the estimation of effective parameters—a kind of integral macroscopic characteristic of media mostly used for composite materials with inclusions. To achieve this, we approximate real geological media with layered bianisotropic media, employing the effective media approximation (EMA) averaging technique to simplify the retrieval of the effective electromagnetic parameters (e.g., apparent resistivity–inversely proportional to electrical conductivity). Additionally, we investigate the correlation between effective electromagnetic parameters and geodynamic processes, which is supported by the experimental data obtained during monitoring studies in the Tien Shan region. The observed decrease and increase in apparent electrical resistivity values of ρk over time in orthogonal azimuths leads to further ρk deviations of up to 80%. We demonstrate that transitioning to another coordinate system is equivalent to considering gradient anisotropic media. Building upon the developed method, we derive the effective electric conductivity tensor for gradient anisotropic media by modeling the process of fracturing in a rock mass. Research findings validate the concept that continuous electromagnetic monitoring can aid in identifying natural geodynamic disasters based on variations in integral macroscopic parameters such as electrical conductivity. The geodynamic processes are closely related to seismicity and stress regimes with provided constraints. Therefore, disasters such as earthquakes are damaging and seismically hazardous.