scholarly journals Magnetic effects due to earthquakes and underground explosions: a review

1997 ◽  
Vol 40 (2) ◽  
Author(s):  
V. V. Surkov ◽  
V. A. Pilipenko
Keyword(s):  
Magnetic Induction ◽  
Geomagnetic Field ◽  
Seismic Waves ◽  
Physical Nature ◽  
Earth’S Crust ◽  
Magnetic Effects ◽  
Tsunami Detection ◽  
Electromagnetic Effects ◽  
Earth's Crust ◽  
Theoretical Results

The physical nature of quasi-static and transient anomalies in the geomagnetic field induced by underground explosions or earthquakes is reviewed. New theoretical results obtained recently and so far little known to general circles of geophysicists are presented. The physical nature of residual magnetic and electrotelluric fields at the explosion point are considered. The seismic waves from explosions or distant earthquakes are suggested to be used as a tool for the preliminary probing of the Earth's crust sensitivity to various seismo-electromagnetic effects. The use of magnetic induction effects for tsunami detection and for crust sounding is outlined. The nature of ULF magnetic impulses related with earthquakes is discussed.

scholarly journals Simulation of seismic waves at the earth's crust (brittle–ductile transition) based on the Burgers model

Solid Earth ◽  
2014 ◽  
Vol 5 (2) ◽  
pp. 1001-1010 ◽  
Author(s):  
J. M. Carcione ◽  
F. Poletto ◽  
B. Farina ◽  
A. Craglietto
Keyword(s):  
Seismic Waves ◽  
In Situ Stress ◽  
Seismic Attenuation ◽  
Earth’S Crust ◽  
S Wave ◽  
Fourier Pseudospectral Method ◽  
Stress Criterion ◽  
Brittle Ductile Transition ◽  
Earth's Crust

Abstract. The earth's crust presents two dissimilar rheological behaviors depending on the in situ stress-temperature conditions. The upper, cooler part is brittle, while deeper zones are ductile. Seismic waves may reveal the presence of the transition but a proper characterization is required. We first obtain a stress–strain relation, including the effects of shear seismic attenuation and ductility due to shear deformations and plastic flow. The anelastic behavior is based on the Burgers mechanical model to describe the effects of seismic attenuation and steady-state creep flow. The shear Lamé constant of the brittle and ductile media depends on the in situ stress and temperature through the shear viscosity, which is obtained by the Arrhenius equation and the octahedral stress criterion. The P and S wave velocities decrease as depth and temperature increase due to the geothermal gradient, an effect which is more pronounced for shear waves. We then obtain the P−S and SH equations of motion recast in the velocity-stress formulation, including memory variables to avoid the computation of time convolutions. The equations correspond to isotropic anelastic and inhomogeneous media and are solved by a direct grid method based on the Runge–Kutta time stepping technique and the Fourier pseudospectral method. The algorithm is tested with success against known analytical solutions for different shear viscosities. A realistic example illustrates the computation of surface and reverse-VSP synthetic seismograms in the presence of an abrupt brittle–ductile transition.

scholarly journals Transient electromagnetic radiation of the lithosphere in a seismically active region

2019 ◽  
Vol 127 ◽  
pp. 03006
Author(s):  
Yiyang Luo ◽  
Nguyen Xuan An ◽  
Vladislav Lutsenko ◽  
Vladimir Uvarov
Keyword(s):  
Electromagnetic Field ◽  
Active Region ◽  
Electromagnetic Radiation ◽  
Seismic Waves ◽  
Earth’S Crust ◽  
Schumann Resonance ◽  
Short Term ◽  
Transient Electromagnetic ◽  
Earth's Crust ◽  
High Level

To study the electromagnetic radiation of the lithosphere associated with seismic waves, we used the recordings of the natural electromagnetic radiation obtained under conditions of weak industrial noise and a high level of microseismicity in the ELF-VLF wave bands. It is shown that these data contain information about the surface waves of the Earth’s crust and are accompanied by a frequency close to the first harmonic of the Schumann resonance. The distribution of spikes over thresholds is obtained, which can be indicators of the activity in the processes of the Earth’s crust. The averaged form of the spikes for different components of the electromagnetic field is obtained. Attention is drawn to the differences in the various components of the electromagnetic field and their diurnal differences are analyzed. The possibility of using the approach to predict the short-term movement of the Earth’s crust is considered.

scholarly journals Variable Mantle Lies Below Ancient Pieces of Earth's Crust

Eos ◽  
2016 ◽  
Vol 97 ◽  
Author(s):  
Cody Sullivan
Keyword(s):  
North America ◽  
Seismic Waves ◽  
Earth’S Crust ◽  
Earth's Crust ◽  
Uppermost Portion

Underneath old and stable pieces of Earth's crust in North America, the mantle's uppermost portion contains multiple layers that change the velocities of seismic waves.

scholarly journals Analysis of the features of the spatio-temporal distribution of geoelectric inhomogeneities in the Earth’s crust and seismic events

2021 ◽  
Vol 254 ◽  
pp. 02003
Author(s):  
Elena Bataleva
Keyword(s):  
Temporal Distribution ◽  
Physical Nature ◽  
Tien Shan ◽  
Earth’S Crust ◽  
Seismic Events ◽  
Magnetotelluric Data ◽  
Geological Conditions ◽  
Spatio Temporal ◽  
Earth's Crust ◽  
The Relationship

The paper presents the results of experiments carried out at the regime points of magnetotelluric monitoring both on the territory of the Bishkek geodynamic test site (Northern Tien Shan) and on a series of monitoring profiles in various geological conditions. Previous studies indicate the relationship of variations in the electromagnetic and seismic fields, lunisolar tidal effects, seismic regime with the processes of fracturing. The purpose of this work is to establish the features of the relationship between the spatio-temporal distribution of seismicity and the distribution of geoelectric inhomogeneities in the Earth’s crust (fault-block tectonics of the region). Based on the analysis of the results of the interpretation of magnetotelluric data (2D inversion) and new detailed seismotomographic constructions, the verification of geoelectric models was carried out, the analysis of the distribution of hypocenters of seismic events was carried out. Special attention was paid to the confinement of earthquakes to listric fault structures. The relationship between the distribution of the hypocenters of seismic events and the spatial position of the electrical conductivity anomalies is confirmed by the authors explanation of the physical nature of the identified conducting structures, based on hypotheses of fluidization and partial melt of the Earth’s crust.

On the calculation of AFMAG *AFMAG—Audio Frequency Magnetics.anomalies

Geophysics ◽  
1960 ◽  
Vol 25 (6) ◽  
pp. 1290-1293
Author(s):  
JAMES Richard WAIT
Keyword(s):  
Geomagnetic Field ◽  
The Other ◽  
Earth’S Crust ◽  
Audio Frequency ◽  
Geophysical Prospecting ◽  
Frequency Range ◽  
Horizontal Stratification ◽  
Charles Wright ◽  
Earth's Crust ◽  
Practical Scheme

It has been proposed by S. H. Ward (1959) and C. S. Wright et al. (1960) that nonuniformity in the earth's crust will tend to tilt the direction of the fluctuating components of the geomagnetic field from its normal horizontal direction. In fact, Ward and colleagues have developed a practical scheme (AFMAG) for geophysical prospecting which makes use of this phenomenon in the frequency range from 100 to 400 c/s. Sir Charles Wright et al., on the other hand, have found that at much lower frequencies, .005 to 1 c/s, a substantial verticalcomponent of the field in the vicinity of coast lines or other situations where the earth's crust departs from horizontal stratification.

Structure et Propriétés Physiques de l'Écorce Terrestre en Fenno-Scandinavie

1972 ◽  
Vol 9 (4) ◽  
pp. 339-352 ◽  
Author(s):  
Maurice K. Seguin
Keyword(s):  
Seismic Data ◽  
Seismic Waves ◽  
Earth’S Crust ◽  
Tectonic Activity ◽  
Seismic Events ◽  
Work Related ◽  
Global Geodynamics ◽  
Propriétés Physiques ◽  
Earth's Crust ◽  
East West

The author completely reviews previous geophysical work related to the nature and structure of the earth's crust in Fennoscandia. He explains the analytical procedure used for the seismic data and the method used to locate seismic events in Fennoscandia. Having described the method of analysis, the procedure for the calculation of the velocity of the seismic waves, and the location of seismic events which originate from Fennoscandia as well as the characteristics of the seismic waves registered, the author calculates the thickness of 3 layers which constitute the earth's crust at various localities in Fennoscandia and drafts a spatial distribution for the thickness of each of these layers. The first order variations, which agree with the relative thickness of the layers, indicate the presence of a generally east-west gradient. A general thinning of the crust was observed to the west in Fennoscandia. In view of the results obtained, the author draws conclusions relative to the tectonic activity and the global geodynamics in Fennoscandia.

scholarly journals Pre-earthquake magnetic pulses

2015 ◽  
Vol 15 (8) ◽  
pp. 1873-1880 ◽  
Author(s):  
J. Scoville ◽  
J. Heraud ◽  
F. Freund
Keyword(s):  
Magnetic Field ◽  
Earth’S Crust ◽  
System Of Equations ◽  
Transient Currents ◽  
Drift Diffusion ◽  
Electrical Currents ◽  
Long Wavelength ◽  
Electromagnetic Effects ◽  
Pass Through ◽  
Earth's Crust

Abstract. A semiconductor model of rocks is shown to describe unipolar magnetic pulses, a phenomenon that has been observed prior to earthquakes. These pulses are suspected to be generated deep in the Earth's crust, in and around the hypocentral volume, days or even weeks before earthquakes. Their extremely long wavelength allows them to pass through kilometers of rock. Interestingly, when the sources of these pulses are triangulated, the locations coincide with the epicenters of future earthquakes. We couple a drift-diffusion semiconductor model to a magnetic field in order to describe the electromagnetic effects associated with electrical currents flowing within rocks. The resulting system of equations is solved numerically and it is seen that a volume of rock may act as a diode that produces transient currents when it switches bias. These unidirectional currents are expected to produce transient unipolar magnetic pulses similar in form, amplitude, and duration to those observed before earthquakes, and this suggests that the pulses could be the result of geophysical semiconductor processes.

scholarly journals The Reference System in Determining the Parameters of Horizontal Deformations of the Earth's Crust on Geodynamic Polygons

2019 ◽  
Vol 8 (2S11) ◽  
pp. 3867-3871
Keyword(s):  
Initial Data ◽  
Reference System ◽  
Related Problem ◽  
Physical Nature ◽  
Theory Of Elasticity ◽  
Reference Points ◽  
Earth’S Crust ◽  
Measuring Instruments ◽  
Data Errors ◽  
Earth's Crust

The article is devoted to the choice of the reference system and the related problem of initial data errors while determining the features of the earth's crustal deformations, determined at the geodynamic polygons (GDP) by the differences of the equalized coordinates of network points between the geodetic measurements epochs. It is shown that the problem is not eliminated in the transition to satellite measuring instruments. In determining the geometric component of the earth's crust deformations, it is recommended to take into account the physical nature of its origin. To ensure the uniformity of the reference system for all geodesic measurements epochs on the local GDPs it is recommended to use the free geodetic networks equalization device without reference points. The deformation components obtained according to the theory of elasticity should be recognized the priority features of the earth's crust deformations on such GDPs.

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