scholarly journals Improving of electrical channels for magnetotelluric sounding instrumentation

2015 ◽  
Vol 4 (2) ◽  
pp. 149-154 ◽  
Author(s):  
A. M. Prystai ◽  
V. O. Pronenko
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Deep Structure ◽  
Experimental Tests ◽  
Magnetotelluric Sounding ◽  
Earth’S Crust ◽  
Geomagnetic Variations ◽  
The Earth ◽  
Wide Range ◽  
Earth's Crust

Abstract. The study of the deep structure of the Earth's crust is of great interest for both applied (e.g. mineral exploration) and scientific research. For this the electromagnetic (EM) studies which enable one to construct the distribution of electrical conductivity in the Earth's crust are of great use. The most common method of EM exploration is magnetotelluric sounding (MT). This passive method of research uses a wide range of natural geomagnetic variations as a powerful source of electromagnetic induction in the Earth, producing telluric current variations there. It includes the measurements of variations of natural electric and magnetic fields in orthogonal directions at the surface of the Earth. By this, the measurements of electric fields are much more complicated metrological processes, and, namely, they limit the precision of MT prospecting. This is especially complicated at deep sounding when measurements of long periods are of interest. The increase in the accuracy of the electric field measurement can significantly improve the quality of MT data. Because of this, the development of a new version of an instrument for the measurements of electric fields at MT – both electric field sensors and the electrometer – with higher levels relative to the known instrument parameter level – was initiated. The paper deals with the peculiarities of this development and the results of experimental tests of the new sensors and electrometers included as a unit in the long-period magnetotelluric station LEMI-420 are given.

scholarly journals Improving of electrical channels for magnetotelluric sounding instrumentation

2015 ◽  
Vol 5 (1) ◽  
pp. 63-81
Author(s):  
A. M. Prystai ◽  
V. O. Pronenko
Keyword(s):  
Electric Field ◽  
Deep Structure ◽  
Mineral Exploration ◽  
Experimental Tests ◽  
Magnetotelluric Sounding ◽  
Earth’S Crust ◽  
Geomagnetic Variations ◽  
The Earth ◽  
Wide Range ◽  
Earth's Crust

Abstract. The study of deep structure of the Earth's crust is of great interest for both applied (e.g. mineral exploration) and scientific research. For this the electromagnetic (EM) studies which enable to construct the distribution of electrical conductivity in the Earth's crust are of great use. The most common method of EM exploration is magnetotelluric sounding (MT). This passive method of research uses a wide range of natural geomagnetic variations as a powerful source of electromagnetic induction in the Earth, producing there telluric currents variations. It includes the measurements of variations of natural electric and magnetic fields in orthogonal directions at the surface of the Earth. By this, the measurements of electric field are much more complicated metrological process, and namely they are limiting the precision of MT prospecting. This is especially complicated at deep sounding when measurements of long periods are of interest. The increase of the accuracy of the electric field measurement can significantly improve the quality of MT data. Because of this the development of new version of instrument for the measurements of electric field at MT – both electric field sensors and the electrometer – with higher relative to the known instruments parameters level were initiated. The paper deals with the peculiarities of this development and the results of experimental tests of the new sensors and electrometer included as a unit in the long-period magnetotelluric station LEMI-420 are given.

scholarly journals Structure of the Earth crust and upper mantle along seismological profile Mezen–Timan–Pechora (MEZTIMPECH)

LITOSFERA ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 517-527
Author(s):  
V. V. Udoratin
Keyword(s):  
Upper Mantle ◽  
Deep Structure ◽  
Structural Features ◽  
Earth’S Crust ◽  
Seismic Section ◽  
Crust And Upper Mantle ◽  
Research Results ◽  
The Earth ◽  
Geophysical Surveys ◽  
Earth's Crust

Object of study. The article was devoted to investigation of the depth structure of the Earth’s crust and upper mantle along the Mezen–Timan–Pechora seismic profile (MEZTIMPECH), crossing the southern parts of the Mezen syneclise, the Timan ridge and the Pechora syneclise. Total profile length was 525 km. Materials and methods. In the course of writing the article, the data obtained by performing seismic surveys using the earthquake exchange wave method were used. The processing involved seismic data using the methods of deep seismic sounding, reflected waves, a common depth point, a correlated method of refracted waves, and materials from well geophysical surveys. In interpreting the research results, generalizing models of the deep structure of the territory were employed. Research results. As a result of the interpretation of the records of the method of exchange waves of earthquakes and the subsequent mathematical modeling, a geological and geophysical section was constructed to a depth of about 100 km and a number of seismic boundaries were identified. The pivotal boundaries of the exchange were: Ф0 – the surface of the Riphean folded basement, Ф – the surface of the pre-Riphean crystalline basement, M – the surface of Mohorovich, identified with the roof of the upper mantle. Additionally, horizons K1–K4 – in the crust of the Earth, M1, M2 – in the upper mantle were traced. Four regional geoblocks were distinguished in the seismic section, differing in depth of the basement surface, the Moho sectionand the underlying structural features of the consolidated crust: the Kirov-Kazhim aulacogen, the Vychegda depression, the Timan ridge and the Pre-Ural downfold. Conclusions. The results of deep seismic studies reflected regional features of the structure of the Earth’s crust and were the basis for the construction of tectonic models of large geological objects.

DIPOLE METHOD FOR DEEP RESISTIVITY STUDlES

Geophysics ◽  
1966 ◽  
Vol 31 (6) ◽  
pp. 1088-1104 ◽  
Author(s):  
G. V. Keller
Keyword(s):  
Electrical Properties ◽  
Electric Field ◽  
Electrical Current ◽  
Earth’S Crust ◽  
Electrode Arrays ◽  
The Earth ◽  
Spacing Factor ◽  
Earth's Crust ◽  
Principal Advantage

The dipole method of measuring resistivity is practical for use in studying the electrical properties of the earth’s crust. In such studies, electrical current is driven into the ground with a pair of electrodes spaced a few kilometers apart, and the electric field caused by this current is mapped to distances as great as 100 km. The principal advantage of the dipole method is the relatively small amount of cable which has to be laid out in comparison with that required by other electrode arrays. The results obtained from dipole surveys are very similar to the results obtained from other arrays, provided that the spacing factor is defined in an appropriate way, and that the earth is laterally homogeneous. If the electrical properties of the earth vary laterally, the dipole method provides results which differ widely from the data obtained with other arrays. This sensitivity to lateral effects is probably the most serious drawback to the use of dipole methods in crustal resistivity surveys.

scholarly journals INQUIRY INTO VERTICAL MOVEMENTS OF THE EARTH‘S CRUST BASED ON SAMPLES FROM EASTERN LITHUANIA

2014 ◽  
Vol 40 (2) ◽  
pp. 58-67
Author(s):  
Ruta Puziene ◽  
Asta Anikeniene ◽  
Gitana Karsokiene
Keyword(s):  
Regression Models ◽  
Earth’S Crust ◽  
Movement Velocity ◽  
Correlation Matrices ◽  
Vertical Movements ◽  
Statistical Correlations ◽  
Horizontal Gradients ◽  
The Earth ◽  
Earth's Crust ◽  
Made In

In the research of vertical movements of the earth’s crust, examination of statistical correlations between the measured vertical movements of the earth’s crust and territorial geo-indexes is accomplished with the help of mathematical statistical analysis. Availability of the precise repeated levelling measuring data coupled with the preferred research methodology offer a chance to determine and predict recent vertical movements of the earth’s crust. For the inquiry into recent vertical movements of the earth’s crust, a Lithuanian class I vertical network levelling polygon was used. Drawing on measurements made in the polygon, vertical velocities of earth’s crust movements were calculated along the following levelling lines. For determining the relations shared by vertical movements of the earth’s crust and territorial geo-parameters, the following territory-defining parameters are accepted. Examination of the special qualities of relations shared by vertical movements of the earth’s crust and geo-parameters in the territory under research contributed to the computation of correlation matrices. Regression models are worked out taking into consideration only particular territory-defining geo-parameters, i.e. only those parameters which exhibit the following correlation coefficient value of the vertical earth’s crust movement velocity: r ≥ 0.50. A forecast of the velocities pertaining to vertical movements of the earth’s crust in the territory under examination was made with the application of regression models. Further in the process of this research, a map was compiled specifying the velocities of vertical movements of the earth’s crust in the territory. In the eastern part of this territory, the earth’s crust rises at a rate of up to 3 mm/year; while in the western part of it, the earth crust lowers at a rate of up to –1.5 mm/year. In order to pinpoint territories characterised by temperate and regular rising/lowering or intensive rising/lowering, a map of horizontal gradients of recent vertical earth crust movements in the territory enclosed by levelling polygon was compiled.

The vibration of electrified water drops

1971 ◽  
Vol 322 (1551) ◽  
pp. 523-534 ◽  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Axial Ratio ◽  
Uniform Electric Field ◽  
Interferometric Technique ◽  
Photographic Analysis ◽  
Wide Range ◽  
Water Drops ◽  
Strength And Deformation ◽  
A Charge

Pressure has been used as the principal parameter in calculations of the fundamental vibrational frequencies of spherical drops of radius R , density ρ, and surface tension T carrying a charge Q or uncharged spheroidal drops of axial ratio a / b situated in a uniform electric field of strength E . Freely vibrating charged drops have a frequency f = f 0 ( 1 - Q 2 /16π R 3 T ) ½ , as shown previously by Rayleigh (1882) using energy considerations; f 0 is the vibrational frequency of non-electrified drops (Rayleigh 1879). The fundamental frequency of an uncharged drop in an electric field will decrease with increasing field strength and deformation a / b and will equal zero when E ( R )/ T ) ½ = 1.625 and a / b = 1.86; these critical values correspond to the disintegration conditions derived by Taylor (1964). An interferometric technique involving a laser confirmed the accuracy of the calculations concerned with charged drops. The vibration of water drops of radius around 2 mm was studied over a wide range of temperatures as they fell through electric fields either by suspending them in a vertical wind tunnel or allowing them to fall between a pair of vertical electrodes. Photographic analysis of the vibrations revealed good agreement between theory and experiment over the entire range of conditions studied even though the larger drops were not accurately spheroidal and the amplitude of the vibrations was large.

scholarly journals Deep structure and geodynamic conditions of granitoid magmatism in the Eastern Russia

2020 ◽  
Vol 243 ◽  
pp. 259
Author(s):  
Viktor Alekseev
Keyword(s):  
Deep Structure ◽  
Gravity Anomalies ◽  
Federal District ◽  
Heat Fluxes ◽  
Earth’S Crust ◽  
Granitoid Magmatism ◽  
The Pacific ◽  
Earth's Crust ◽  
Far Eastern ◽  
Eastern Russia

We investigated the deep structure of the lithosphere and the geodynamic conditions of granitoid magmatism in the Eastern Russia within the borders of the Far Eastern Federal District. The relevance of the work is determined by the need to establish the geotectonic and geodynamic conditions of the granitoids petrogenesis and ore genesis in the Russian sector of the Pacific Ore Belt. The purpose of the article is to study the deep structure of the lithosphere and determine the geodynamic conditions of granitoid magmatism in the East of Russia. The author's data on the magmatism of ore regions, regional granitoids correlations, archive and published State Geological Map data, survey mapping, deep seismic sounding of the earth's crust, gravimetric survey, geothermal exploration, and other geophysical data obtained along geotraverses. The magma-controlling concentric geostructures of the region are distinguished and their deep structure is studied. The connection of plume magmatism with deep structures is traced. The chain of concentric geostructures of Eastern Russia controls the trans-regional zone of leucocratization of the earth's crust with a width of more than 1000 km, which includes the Far Eastern zone of Li-F granites. Magmacontrolling concentric geostructures are concentrated in three granitoid provinces: Novosibirsk-Chukotka, Yano-Kolyma, and Sikhote-Alin. The driving force of geodynamic processes and granitoid magmatism was mantle heat fluxes in the reduced zones of the lithospheric slab. The distribution of slab windows along the Pacific mobile belt's strike determines the location of concentric geostructures and the magnitude of granitoid magmatism in the regional provinces. Mantle diapirs are the cores of granitoid ore-magmatic systems. The location of the most important ore regions of the Eastern Russia in concentric geostructures surrounded by annuli of negative gravity anomalies is the most important regional metallogenic pattern reflecting the correlation between ore content and deep structure of the earth's crust.

Metamorphic Rocks

2018 ◽  
Author(s):  
Alex Maltman
Keyword(s):  
Metamorphic Rock ◽  
Central Area ◽  
Tectonic Stress ◽  
Earth’S Crust ◽  
Metamorphic Rocks ◽  
Tectonic Plates ◽  
The Earth ◽  
Two Factors ◽  
Earth's Crust ◽  
Increased Pressure

We come now to the metamorphic rocks, the result of modifications to already existing rock. I’m well aware that this can all seem a bit mysterious. After all, no one has ever seen the changes take place; no one has ever witnessed a metamorphic rock form—the processes are imperceptibly slow, and they happen deep in the Earth’s crust, way out of sight. Why should these changes happen? Well, they are primarily driven by increases in pressure and temperature, so we begin with a look at these two factors. There are sites in the Earth’s crust where material becomes progressively buried. It happens, for example, where a tectonic plate is driving underneath another one, taking rocks ever deeper as it descends. It can happen in the central area of a plate that is stretching and sagging, allowing thick accumulations of sediment. It’s pretty self-evident that as buried material gets deeper, because of the growing weight of rocks above bearing down due to gravity, it becomes subjected to increasing burial pressure. Less intuitive, though, is the fact that this pressure acts on a volume of rock equally in all directions. Imagine a small volume of rock at depth. It’s bearing the weight of the rocks above it, and so it responds by trying to move downward and to spread out laterally. Of course, it can’t because it’s constrained all around by other volumes of rock that are trying to do exactly the same thing. And so the downward gravity is translated into an all-around pressure. It’s the same effect as diving down to the bottom of a swimming pool. You feel the increased pressure owing to the weight of water above, but you feel it equally in all directions. All-round pressure like this can cause things to change in volume, through changing their density, but it can’t change their shape. However, there can be another kind of pressure as well, and this does have direction, and it can cause change of shape. In the Earth, we call it tectonic stress. It comes about through heat-driven motions in the Earth, including the movement of tectonic plates.

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