M. G. Dembelov

Experimental proof of the existence of a surface electromagnetic wave

Results of experiments for the observation of surface electromagnetic waves (SEWs) in the decameter range (10 and 15 MHz) excited by a vertical dipole and propagating above the ice-coated surface of a salt lake over a distance of up to 1.2 km are considered. It is shown that the SEW decays much more weakly than the “ground” ray. An analysis of the field of radiation from the vertical dipole reveals the presence of a wave with an amplitude decaying with the distance R approximately as 1/R1/2, which corresponds to the SEW divergence. The absolute values of the radiation attenuation function |W| are significantly greater than unity and reach |W| ≈ 2, which also corresponds to the SEW. Experimental data on the SEW damping agree with the results of numerical calculations of the electromagnetic field in the system under consideration.

Contemporary horizontal movements and seismicity of the south Baikal Basin (Baikal rift system)

The contemporary horizontal movements and deformations in the central and southern parts of the Baikal depression are analyzed, and their relationship with contemporary seismicity is studied. Based on the long-term measurements by the Baikal geodynamical GPS monitoring network, the refined estimate is obtained for the velocity of the divergence of the Siberian and Transbaikalian blocks, which is found to occur in the southeastward direction (130°) at 3.4 ± 0.7 mm per annum. This agrees with the parameters of the long-term extension component estimated from the geological data and with the direction of extension determined from the seismic data. The distribution of the displacement velocity across the strike of the rift, which gradually increases from one block to another, suggests a nonrigid behavior of the continental lithospheric plates at the divergent boundary. About 30% (1.0–1.5 mm per annum) of the total increase in the velocity is accommodated by the Baikal Basin. The strain rate within the trough reaches 3.1 × 10−8 yr−1 and decreases on either side across the structure. The character of distribution of the horizontal displacement velocities on the Baikal divergent boundary between the Eurasian and Amurian plates favors the model of passive rifting. The zones of highly contrasting topography and increased seismicity are localized within the area of contemporary deformations, and the seismic moment release rate directly depends on the strain rate. Here, the rate of the seismic moment release rate makes up a few percent of the geodetic moment accumulation rate calculated by the approach suggested by Anderson (1979). Based on the coherence between the graphs of the rates of geodetic moment accumulation and seismic moment release rate by the earthquakes with M ≥ 5.0 during the historical and instrumental observation periods, the contemporary seismic hazard for the South Baikal Basin could be assessed at a level of seismic event with M = 7.5–7.6.

Effect of the cryolithic zone electrical properties on the medium-frequency surface wave at high latitudes

Result of the measurements of the cryolithic zone electrical properties by the radio impedance sounding method are presented. The surface impedance and geoelectric section of the Arctic permafrost have been determined. The experiments have been performed near Cherskii in the continental zone. The surface wave attenuation function is considered. The accuracy of the surface wave field calculations at high latitudes has been estimated based on the local electrical characteristics of the underlying cryogenic medium. The effect of the Arctic Ocean on the operating zone of navigation and communication facilities in the kilometer wave band has been experimentally estimated.

Restoration of a two-layer geoelectric section in the coastal area of Lake Baikal

Radioimpedance measurements are taken at two sites on ice in the coastal area of Lake Baikal. From these full-scale measurements for a water-bottom soil system, a two-layer geoelectric section is restored; namely, the resistivities of a water layer and bottom soil are determined and the thickness of the water layer is measured. For example, the following values are obtained at one of the sites: water resistivity ρw = 120 Ω m, bottom soil resistivity ρb = 1400 Ω m, and depth h = 5.5 m. These values are in agreement with published data. The suggested method or geoelectric section restoration is applicable to a thin water layer near the coast.

Electromagnetic waves over stratified media in natural conditions

Experimental data of the radio wave propagation over high inductive structure “ice-salt water” in the decameter range of a field radiated by vertical dipole on a distance of up to 1.2 km are considered. It is shown that the surface electromagnetic waves (SEW) were attenuated less than the “ground” ray. An analysis of the field of radiation from the vertical dipole reveals the presence of a wave with the amplitude decaying with the distance R approximately as 1/R1/2, which corresponds to the SEW divergence. The absolute values of the radiation attenuation function |W| are significantly greater than unity and reach |W|=2, which also corresponds to the SEW. Experimental data on the SEW damping agree with the results of numerical calculations of the electromagnetic field in the system under consideration.

Electrometric method to determine the surface impedance of an ice–sea water bilayer system

An electrometric method to determine the surface impedance of an ice–sea water bilayer system is suggested. The complex impedance (its magnitude and phase) of this system is determined at very low, low, and medium frequencies from electrometric, rather than radio, measurements. For the ice–sea water system, it is sufficient to determine the conductivity and thickness of a water sample from drilling data.

Diagnostics of atmospheric water vapor content according to GPS measurements

A continuously operating GPS network, comprising seven permanent observation sites, is created to study the geodynamic processes in the Baikal region. Processing of the initial GPS data provides continuous atmospheric data in the form of total zenith tropospheric delay, which can be used for meteorological and climatological studies. The total delay is the sum of “dry”, or hydrostatic, and “wet” components. The wet component determines the total water vapor amount and amount of precipitable water over the measurement site. Thus, GPS measurements make it possible to obtain initial data for creating new numerical models of zenith tropospheric delay and total precipitable water vapor for meteorological applications.

Maps of geoelectric sections of Turkey, Iran, Afghanistan, Pakistan, Korea, and Japan

Results of geoelectric mapping of the some countries of Asia with high seismic activity are presented. The methodology of the geoelectric mapping is considered. Maps of geoelectric sections of Turkey, Iran, Afghanistan, Pakistan, Korea, and Japan on a scale of 1:5 000 000 are constructed. The scale of ρj and hj has three gradations per decade.

An Attenuation Function of the Ground Wave Field Over Two-Dimensional Inhomogeneous Radio Paths

Ground wave field propagation of electromagnetic waves transmitted by a vertical electric dipole in LF-MF ranges is considered. A new method of calculation of an attenuation function of the radio wave propagation taking into account two-dimensional model of inhomogeneities is offered. The solution is in form of totality of one-dimensional attenuation functions within several first Fresnel zones. EM wave propagates over an inhomogeneous irregular surface

Radiophysical Monitoring of the Lake Baikal Ice Cover

Presented are the results of the winter 2014 radiophysical expedition, within the framework of which the Baikal ice cover was investigated by electromagnetic methods. The primary objectives the expedition were to detect irregularities in the ice cover, such as cracks and thawing steamed holes in the ice, and to determine the ice thickness and structure in the area of the thawing holes by the GPR sounding method. We used in the experiments the OKO-2 ground-penetrating radar (GPR) of the decimeter band and the nanosecond radar with the wavelength of 3 cm. The measurements were made carried out from the Khivus hovercraft and from the UAZ automobile. The ice thickness of Lake Baikal was determined by non-contact electromagnetic measurement methods. Radargrams of reflected signals from the ice cover are presented. Radar patterns of reflected signals from artificial irregularities of the ice cover were obtained by the short-pulse radar method. The concept of radiophysical monitoring is suggested, which provides a means of determining the ice cover parameters of a water body with high spatial resolution. We present an integral approach to investigating the conditions of the ice cover in order to integrate different physicochemical methods for diagnosing the objects studied. A further development of the concept of integrated ice cover research, and the creation of the monitoring network involves solving a number of scientific and engineering tasks that include developing physical models and information and measurement systems as well as the rationale for an integrated monitoring network.