scholarly journals Ionospheric influence on the seismo-telluric current related to electromagnetic signals observed before the Wenchuan <i>M</i><sub>S</sub> = 8.0 earthquake

2016 ◽  
Author(s):  
Mei Li ◽  
Handong Tan ◽  
Meng Cao
Keyword(s):  
Current Source ◽  
Ionospheric Effect ◽  
Electrical Fields ◽  
Model Free ◽  
Ionosphere Model ◽  
The Earth ◽  
Main Fault ◽  
Electromagnetic Signals ◽  
The Waves ◽  
Detectability Threshold

Abstract. A three-layer (Earth-air-ionosphere) physical model, as well as a two-layer (Earth-air) model, is employed in this paper to investigate the ionospheric effect on the wave fields for a finite length dipole current source co-located with the main fault of an earthquake when the transmitter-receiver distance is up to one thousand kilometers or even more. The results show that all electrical fields are free of the ionospheric effect for different frequencies in a relative short range, e.g., ~ 300 km for f = 1 Hz, implying the ionospheric influence on electromagnetic fields can be neglected within this range that becomes smaller as the frequency increases. However, the ionosphere can give a constructive interference to the waves passed through and make them decay slowly when an observation is out of this range and the ionosperic effect can be up to 1–2 magnitudes of the electrical fields. For an observed 1.3 mV/m signal at 1,440 km away for the Wenchuan MS = 8.0 earthquake, the expected seismo-telluric current magnitude for the Earth-air-ionosphere model is of 5.0 × 104 kA , which is of one magnitude smaller than the current value of 3.7 × 105 kA obtained by the Earth-air model free of ionospheric effect. This indicates that the ionosphere facilitates the electromagnetic wave propagation, as if the detectability of the system is improved effectively and it is easier to record a signal even for stations located at distances beyond their detectability threshold.

scholarly journals Ionospheric influence on the seismo-telluric current related to electromagnetic signals observed before the Wenchuan <i>M</i><sub><i>S</i></sub> 8.0 earthquake

Solid Earth ◽  
2016 ◽  
Vol 7 (5) ◽  
pp. 1405-1415 ◽  
Author(s):  
Mei Li ◽  
Handong Tan ◽  
Meng Cao
Keyword(s):  
Power Distribution ◽  
Current Source ◽  
Electric Signal ◽  
Ionospheric Effect ◽  
Electrical Fields ◽  
Ionospheric Effects ◽  
Model Free ◽  
Ionosphere Model ◽  
The Earth ◽  
Electromagnetic Signals

Abstract. A three-layer (Earth–air–ionosphere) physical model, as well as a two-layer (Earth–air) model, is employed in this paper to investigate the ionospheric effect on the wave fields for a finite length dipole current source co-located at a hypocenter depth and along the main fault of an earthquake when the distance between the epicenter and an observing station is up to 1000 km or even more. The results show that all electrical fields are free of ionospheric effects for different frequencies in a relative short range, e.g.,  ∼  300 km for f =  1 Hz, implying the ionospheric influence on electromagnetic fields can be neglected within this range, which becomes smaller as the frequency increases. However, the ionosphere can give a constructive interference to the waves passing through and make them decay slowly when an observation is out of this range; moreover, the ionospheric effect can be up to 1–2 orders of magnitude of the electrical fields. For a ground-based observable 1.3 mV m−1 electric signal at f =  1 Hz 1440 km away from the Wenchuan MS 8.0 earthquake, the expected seismo-telluric current magnitude for the Earth–air–ionosphere model is of 5.0  ×  107A, 1 magnitude smaller than the current value of 3.7  ×  108A obtained by the Earth–air model free of ionospheric effects. This indicates that the ionosphere facilitates the electromagnetic wave propagation, as if the detectability of the system were improved effectively and it is easier to record a signal even for stations located at distances beyond their detectability thresholds. Furthermore, the radiating patterns of the electrical field components |Ex| and |Ey| are complementary to each other, although any two-dimensional (2-D) power distribution of these components shows strong power areas as well as weak ones, which is advantageous to register a signal if the observing system is designed to measure both of them instead of only one.

scholarly journals Estimating the seismotelluric current required for observable electromagnetic ground signals

2010 ◽  
Vol 28 (8) ◽  
pp. 1615-1624 ◽  
Author(s):  
J. Bortnik ◽  
T. E. Bleier ◽  
C. Dunson ◽  
F. Freund
Keyword(s):  
Simple Model ◽  
Current Source ◽  
Signal Power ◽  
Earthquake Hypocenter ◽  
Detectable Range ◽  
Source Current ◽  
Cardinal Directions ◽  
Electromagnetic Signals ◽  
Ground Conductivity ◽  
Detectability Threshold

Abstract. We use a relatively simple model of an underground current source co-located with the earthquake hypocenter to estimate the magnitude of the seismotelluric current required to produce observable ground signatures. The Alum Rock earthquake of 31 October 2007, is used as an archetype of a typical California earthquake, and the effects of varying the ground conductivity and length of the current element are examined. Results show that for an observed 30 nT pulse at 1 Hz, the expected seismotelluric current magnitudes fall in the range ~10–100 kA. By setting the detectability threshold to 1 pT, we show that even when large values of ground conductivity are assumed, magnetic signals are readily detectable within a range of 30 km from the epicenter. When typical values of ground conductivity are assumed, the minimum current required to produce an observable signal within a 30 km range was found to be ~1 kA, which is a surprisingly low value. Furthermore, we show that deep nulls in the signal power develop in the non-cardinal directions relative to the orientation of the source current, indicating that a magnetometer station located in those regions may not observe a signal even though it is well within the detectable range. This result underscores the importance of using a network of magnetometers when searching for preseismic electromagnetic signals.

scholarly journals Study of Geo-Electric Data Collected by the Joint EMSEV-Bishkek RS-RAS Cooperation: Possible Earthquake Precursors

Entropy ◽  
2018 ◽  
Vol 20 (8) ◽  
pp. 614
Author(s):  
Konstantina Papadopoulou ◽  
Efthimios Skordas ◽  
Jacques Zlotnicki ◽  
Toshiyasu Nagao ◽  
Anatoly Rybin
Keyword(s):  
Epicentral Distance ◽  
Current Source ◽  
Earthquake Precursors ◽  
The Other ◽  
Electric Signal ◽  
Seismic Events ◽  
The Earth ◽  
Subsurface Resistivity ◽  
Telluric Currents ◽  
Electric Current Source

By employing the cross-correlogram method, in geo-electric data from the area of Kyrgyzstan for the period 30 June 2014–10 June 2015, we identified Anomalous Telluric Currents (ATC). From a total of 32 ATC after taking into consideration the electric current source properties, we found that three of them are possible Seismic Electric Signal (SES) activities. These three SES activities are likely to be linked with three local seismic events. Finally, by studying the corresponding recordings when a DC alternating source injects current into the Earth, we found that the subsurface resistivity seems to be reduced before one of these three earthquakes, but a similar analysis for the other two cannot be done due to their large epicentral distance and the lack of data.

Using spacecraft range data and radar observations for the improvement of the orbital elements of planets and parameters of Mars rotation

1996 ◽  
Vol 172 ◽  
pp. 45-48
Author(s):  
E.V. Pitjeva
Keyword(s):  
Major Axis ◽  
Astronomical Unit ◽  
Range Data ◽  
Orbital Elements ◽  
Semi Major Axis ◽  
The Earth ◽  
Electromagnetic Signals ◽  
Least Squares Estimates ◽  
Radar Ranging ◽  
Made In

The extremely precise Viking (1972–1982) and Mariner data (1971–1972) were processed simultaneously with the radar-ranging observations of Mars made in Goldstone, Haystack and Arecibo in 1971–1973 for the improvement of the orbital elements of Mars and Earth and parameters of Mars rotation. Reduction of measurements included relativistic corrections, effects of propagation of electromagnetic signals in the Earth troposphere and in the solar corona, corrections for topography of the Mars surface. The precision of the least squares estimates is rather high, for example formal standard deviations of semi-major axis of Mars and Earth and the Astronomical Unit were 1–2 m.

HIGH‐FREQUENCY ELECTROMAGNETIC COUPLING BETWEEN SMALL COPLANAR LOOPS OVER AN INHOMOGENEOUS GROUND

Geophysics ◽  
1972 ◽  
Vol 37 (6) ◽  
pp. 997-1004 ◽  
Author(s):  
James A. Fuller ◽  
James R. Wait
Keyword(s):  
Half Space ◽  
High Frequency ◽  
Electromagnetic Coupling ◽  
Current Source ◽  
Vertical Axis ◽  
Loop Current ◽  
Mutual Impedance ◽  
Multiplicative Factor ◽  
The Earth ◽  
Horizontal Electric Dipole

An integral formulation is given for the fields of a loop current source which is located over a horizontally stratified half‐space and has a vertical axis. The electrical properties of the half‐space vary exponentially with the depth into the earth. An asymptotic solution is developed for the case of source and observer on the interface but separated by a large numerical distance. The approximate solution is then used to determine the mutual impedance between two small loops and between the loop and a horizontal electric dipole, when the antennas are on the interface. It is found that the effect of stratification on the mutual impedance is represented approximately by a single multiplicative factor.

Why Newtonian gravity is an electromagnetic wave

2020 ◽  
Vol 33 (1) ◽  
pp. 23-26
Author(s):  
Nicolus Rotich
Keyword(s):  
Electromagnetic Wave ◽  
Gravitational Waves ◽  
Newtonian Gravity ◽  
Earth Surface ◽  
Speed Of Light ◽  
The Earth ◽  
Planetary Bodies ◽  
The Waves

In this brief communication, we have hypothesized that since Newtonian gravity intimately interacts with classical gravitational waves, it must also be perceivable and mathematically expressible as a wave. It has been shown that Newtonian gravity can be represented as an electromagnetic wave of a particular wavelength <mml:math display="inline"> <mml:mi>λ</mml:mi> </mml:math> , propagating at the speed of light, c and with a radius of <mml:math display="inline"> <mml:mrow> <mml:mi>z</mml:mi> <mml:mo>=</mml:mo> <mml:mi>λ</mml:mi> <mml:mo>/</mml:mo> <mml:mn>2</mml:mn> <mml:mi>π</mml:mi> </mml:mrow> </mml:math> . The waves period is given by T = c/g, and thus acceleration due to gravity is representable as g = cf, where f is position dependent, and thus unique for all orbiting planetary bodies. On the Earth surface, this value is ≅32.71 nHz.

Microseisms in the 11- to 18-second period range

1957 ◽  
Vol 47 (2) ◽  
pp. 111-127
Author(s):  
Jack Oliver ◽  
Maurice Ewing
Keyword(s):  
Deep Water ◽  
Littoral Zone ◽  
Vertical Component ◽  
Time Correlation ◽  
Period Range ◽  
The Earth ◽  
Seismograph Station ◽  
The Waves ◽  
Second Period ◽  
Wave Recorder

Abstract Storm microseisms in the 11- to 18-second period range recorded at Palisades and Bermuda are attributed to ocean swell of identical periods in the vicinity of the seacoast near the seismograph station. Evidence is based on travel time, correlation with wave-recorder data, and dispersion of the waves from hurricane Dolly, which remained in deep water when near the Palisades station and passed at a speed greater than the group velocity of ocean swell. Ground-particle motion is longitudinal, with little or no vertical component. With some qualifications, the results agree with the classical surf theory of microseism generation. Certainly, the energy is transferred to the earth within the littoral zone.

Memento Mori

2007 ◽  
pp. 55-73
Author(s):  
Gabriel N. Finder ◽  
Judith R. Cohen
Keyword(s):  
Open Pit ◽  
Memento Mori ◽  
The Earth ◽  
The Waves

Still, still, let us be still. Graves grow here. Planted by the enemy, They blossom to the sky.1 I don’t know where your grave is. All the earth is your grave. Under my feet—the waves made by every one of your limbs.2 A photograph of four men sitting in an open pit and contemplating the remains of two human skeletons (...

scholarly journals On the connection between the ray theory of electric waves and dynamics

1931 ◽  
Vol 132 (819) ◽  
pp. 83-98 ◽  
Keyword(s):  
Phase Velocity ◽  
Critical Frequency ◽  
Wave Length ◽  
Ray Theory ◽  
Electronic Density ◽  
Short Waves ◽  
The Earth ◽  
Variable Distribution ◽  
The Waves ◽  
Electric Waves

1. In the study of the transmission of electric waves round the earth (especially in the case of what are now known as short waves of frequencies between 3·3 X 10 7 and 3·3 X 10 6 , 10, to 100 M in wave-length) we have to consider the behaviour of such waves in the ionised region of the upper atmo­sphere. For the purposes of the analysis of the wave motions, this region may be considered as one in which there is a variable distribution of electronic density represented by N ϵ , say, which is taken as a function of the co-ordinates x, y, z . The electronic density is of major importance, the ions, in general, being so heavy that their reaction on the waves is small compared with that of the electrons. The phase velocity V in the medium is then, as is well known, c /√1 — v 0 2 / v 2 where v 0 is the critical frequency of the medium at any point x, y, z given by v 0 2 = N e 2 c 2 /π m , and in respect of this (the quantity N) is a function of the co-ordinates x, y, z . The group velocity U is c √1 — v 0 2 / v 2 , so that UV = c 2 .

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