Analysis of Anisotropic Magnetotelluric Measurements at Victoria, B.C.

1973 ◽  
Vol 10 (4) ◽  
pp. 557-570 ◽  
Author(s):  
W. Nienaber ◽  
D. R. Auld ◽  
H. W. Dosso
Keyword(s):  
Electric Field ◽  
Apparent Resistivity ◽  
Conducting Layer ◽  
Frequency Range ◽  
Entire Frequency Range ◽  
Period Range ◽  
Magnetotelluric Data ◽  
Conductivity Structure ◽  
The University ◽  
Direction Of Polarization

Magnetotelluric data were recorded at the University of Victoria for a wide period range since the summer of 1968. Data for periods between 10 s and 104 s were used for interpretation. Telluric signals were found to be strongly anisotropic for the entire frequency range. Several possible causes of this anisotropy including the land–sea interface and a geological fault at Victoria are discussed.In order to obtain a 'model' for the subsurface conductivity structure, the apparent resistivity curves for both electric field components (E parallel and E perpendicular to the direction of polarization) are combined into one interpretation. The model proposes a thin, highly conducting layer near the surface of a highly resistive earth.The validity of the rotation used in transforming anisotropic telluric data before interpretation was tested experimentally.

Étude régionale magnéto-tellurique des structures de la conductivité électrique sur la bordure occidentale du craton ouest africain en République du Sénégal

1982 ◽  
Vol 19 (7) ◽  
pp. 1408-1416 ◽  
Author(s):  
M. Ritz
Keyword(s):  
Reference Station ◽  
Conducting Layer ◽  
Two Dimensional ◽  
Period Range ◽  
Magnetotelluric Data ◽  
West African Craton ◽  
Magnetotelluric Soundings ◽  
Mobile Stations ◽  
Conductivité Électrique ◽  
Western Border

Magnetotelluric soundings were carried out in the Senegal Republic on the western border of the west African craton by a team of geophysicists from Mbour's Observatory, along an approximately east–west profile. This profile includes four stations about 20 km apart. The purpose of this paper is to analyse and interpret the obtained data. The magnetotelluric data were restricted to a period range of 20–300 s. The measurements were performed individually with a reference station located in the sedimentary basin at approximately 130 km from the craton border, and they allowed one to calculate the amplitude ratios of the electromagnetic field components at the mobile stations. A two-dimensional model indicates the presence of a deep conducting layer at a depth of 80 km for the four stations. For the three stations located on the craton border the introduction of a conducting layer at a depth of 30 km permits a better approximation of the data. On the other hand, the presence of a conducting layer underneath the fourth station located on the craton is not justified by the two-dimensional model.The presence of a conducting zone in the mobile zone crust seems to have resulted from a hydration process. On the craton, the crust became hydrated and the conducting level is not present. [Journal Translation]

Magneto-telluric determination of upper mantle conductivity structure at Victoria, British Columbia

1968 ◽  
Vol 5 (5) ◽  
pp. 1209-1220 ◽  
Author(s):  
B. Caner ◽  
D. R. Auld
Keyword(s):  
Spectral Analysis ◽  
Upper Mantle ◽  
High Resistivity ◽  
Conducting Layer ◽  
Frequency Range ◽  
Tidal Effects ◽  
Conductivity Structure ◽  
Wide Range ◽  
Mantle Conductivity

Magneto-telluric data were obtained at Victoria over a very wide range of periods (2 s to 86 400 s). Only the data up to 15 000 s periods were used for interpretation of conductivity structure, since telluric data at longer periods were dominated by ocean-tidal effects; spectral analysis of one year's data was used to demonstrate the tidal effects. The telluric signals are strongly polarized in the whole frequency range, indicating an anisotropy in surface conductivity.The data indicate the existence of a finite conducting layer 10 ± 3 km thick and resistivity 100–125 ohm-meters, at a depth of 65 ± 5 km. A high resistivity zone (of the order of 4000–5000 ohm-meters) lies below this layer. There is no evidence for any further conducting zones down to a depth of at least 750 km.

scholarly journals Observation evidences of atmospheric Gravity Waves induced by seismic activity from analysis of subionospheric LF signal spectra

2007 ◽  
Vol 7 (5) ◽  
pp. 625-628 ◽  
Author(s):  
A. Rozhnoi ◽  
M. Solovieva ◽  
O. Molchanov ◽  
P.-F. Biagi ◽  
M. Hayakawa
Keyword(s):  
Gravity Waves ◽  
Fresnel Zone ◽  
Signal Amplitude ◽  
Magnetic Storms ◽  
Frequency Range ◽  
Atmospheric Gravity Waves ◽  
Period Range ◽  
Before And After ◽  
Atmospheric Gravity ◽  
Large Earthquakes

Abstract. We analyze variations of the LF subionospheric signal amplitude and phase from JJY transmitter in Japan (F=40 kHz) received in Petropavlovsk-Kamchatsky station during seismically quiet and active periods including also periods of magnetic storms. After 20 s averaging, the frequency range of the analysis is 0.28–15 mHz that corresponds to the period range from 1 to 60 min. Changes in spectra of the LF signal perturbations are found several days before and after three large earthquakes, which happened in November 2004 (M=7.1), August 2005 (M=7.2) and November 2006 (M=8.2) inside the Fresnel zone of the Japan-Kamchatka wavepath. Comparing the perturbed and background spectra we have found the evident increase in spectral range 10–25 min that is in the compliance with theoretical estimations on lithosphere-ionosphere coupling by the Atmospheric Gravity Waves (T>6 min). Similar changes are not found for the periods of magnetic storms.

Introduction of Fine Engineered Domain Configuration into Potassium Niobate Single Crystals

2007 ◽  
Vol 350 ◽  
pp. 89-92
Author(s):  
Keisuke Yokoh ◽  
Tomomitsu Muraishi ◽  
Song Min Nam ◽  
Hirofumi Kakemoto ◽  
Takaaki Tsurumi ◽  
...  
Keyword(s):  
Electric Field ◽  
Single Crystals ◽  
Room Temperature ◽  
Single Domain ◽  
Potassium Niobate ◽  
Field Exposure ◽  
Domain State ◽  
Domain Configuration ◽  
Dc Electric Field ◽  
Direction Of Polarization

To induce fine engineered domain configurations into potassium niobate (KNbO3) single crystals, two kinds of methods were performed, i.e., (1) high DC electric field exposure along the opposite direction of polarization of KNbO3 single-domain crystals at room temperature, and (2) introduction of randomly oriented fine domain configuration by heat treatment at 700 °C and then high DC electric field exposure along [001]c direction of KNbO3 multidomain crystals at room temperature. When the method (1) was performed, finally, the poled KNbO3 crystals became to single-domain state again through the formation of multidomain state. On the other hand, the KNbO3 multidomain crystals were obtained by using the method (2), and an enhancement of piezoelectric-related properties was observed.

Damping and Inertia Coefficients for a Rolling or Swaying Vertical Strip

1963 ◽  
Vol 7 (04) ◽  
pp. 19-23
Author(s):  
J. Kotik
Keyword(s):  
Wave Amplitude ◽  
Added Mass ◽  
Frequency Range ◽  
Entire Frequency Range ◽  
Vertical Strip ◽  
Amplitude Coefficient

Ursell's exact expression3 for the wave-amplitude coefficient for a swaying or rolling vertical strip is evaluated numerically over the entire frequency range. The added-mass and inertia coefficients are then obtained numerically, also over the entire frequency range, via the Kramers-Kronig relations.

Respiratory input impedance in anesthetized paralyzed patients

1990 ◽  
Vol 69 (4) ◽  
pp. 1372-1379 ◽  
Author(s):  
D. Navajas ◽  
R. Farre ◽  
J. Canet ◽  
M. Rotger ◽  
J. Sanchis
Keyword(s):  
Mechanical Model ◽  
Forced Oscillation ◽  
Respiratory Resistance ◽  
Frequency Range ◽  
Entire Frequency Range ◽  
Peripheral Airways ◽  
Distal Branch ◽  
Low Amplitude ◽  
Gas Compressibility ◽  
Central Airway

Respiratory impedance (Zrs) was measured between 0.25 and 32 Hz in seven anesthetized and paralyzed patients by applying forced oscillation of low amplitude at the inlet of the endotracheal tube. Effective respiratory resistance (Rrs; in cmH2O.l-1.s) fell sharply from 6.2 +/- 2.1 (SD) at 0.25 Hz to 2.3 +/- 0.6 at 2 Hz. From then on, Rrs decreased slightly with frequency down to 1.5 +/- 0.5 at 32 Hz. Respiratory reactance (Xrs; in cmH2O.l-1.s) was -22.2 +/- 5.9 at 0.25 Hz and reached zero at approximately 14 Hz and 2.3 +/- 0.8 at 32 Hz. Effective respiratory elastance (Ers = -2pi x frequency x Xrs; in cmH2O/1) was 34.8 +/- 9.2 at 0.25 Hz and increased markedly with frequency up to 44.2 +/- 8.6 at 2 Hz. We interpreted Zrs data in terms of a T network mechanical model. We represented the proximal branch by central airway resistance and inertance. The shunt pathway accounted for bronchial distensibility and alveolar gas compressibility. The distal branch included a Newtonian resistance component for tissues and peripheral airways and a viscoelastic component for tissues. When the viscoelastic component was represented by a Kelvin body as in the model of Bates et al. (J. Appl. Physiol. 61: 873-880, 1986), a good fit was obtained over the entire frequency range, and reasonable values of parameters were estimated. The strong frequency dependence of Rrs and Ers observed below 2 Hz in our anesthetized paralyzed patients could be mainly interpreted in terms of tissue viscoelasticity. Nevertheless, the high Ers we found with low volume excursions suggests that tissues also exhibit plasticlike properties.

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