Coupling of airborne sound into the earth: Frequency dependence

1980 ◽  
Vol 67 (5) ◽  
pp. 1502-1506 ◽  
Author(s):  
H. E. Bass ◽  
L. N. Bolen ◽  
Daniel Cress ◽  
Jerry Lundien ◽  
Mark Flohr
Keyword(s):  
Frequency Dependence ◽  
Airborne Sound ◽  
The Earth

Coupling of airborne sound into the porous elastic surface of the Earth

1983 ◽  
Vol 74 (S1) ◽  
pp. S59-S59
Author(s):  
Henry E. Bass ◽  
Lee N. Bolen ◽  
James M Sabatier
Keyword(s):  
Elastic Surface ◽  
Airborne Sound ◽  
The Earth

Coupling of airborne sound into the earth.

2008 ◽  
Vol 124 (4) ◽  
pp. 2452-2452
Author(s):  
James Sabatier
Keyword(s):  
Airborne Sound ◽  
The Earth

The Frequency Dependence of the Perturbation Fields due to Conductivity Inhomogeneities in the Earth

1973 ◽  
Vol 10 (8) ◽  
pp. 1191-1200 ◽  
Author(s):  
F. W. Jones ◽  
B. A. Ainslie
Keyword(s):  
Frequency Dependence ◽  
Field Component ◽  
Finite Depth ◽  
Infinite Depth ◽  
Perturbation Field ◽  
The Earth

The geomagnetic perturbation fields due to conductivity discontinuities in the Earth are investigated. Two models, one in which the discontinuity extends to infinite depth, and a second one which consists of a dike of finite depth are considered. The perturbation fields are studied for several different frequencies of the alternating inducing field for each model. Both the H-polarization and E-polarization cases are considered and the perturbation field component profiles as a function of height above the surface of the conducting region are studied. The perturbation fields are strongly dependent on frequency, and significant differences are exhibited between the H-polarization and E-polarization cases.

ON THE PROPAGATION OF E.L.F. PULSES IN THE EARTH–IONOSPHERE WAVE GUIDE

1962 ◽  
Vol 40 (10) ◽  
pp. 1360-1369 ◽  
Author(s):  
James R. Wait
Keyword(s):  
Spectral Analysis ◽  
Frequency Dependence ◽  
Time Domain ◽  
Propagation Constant ◽  
Low Frequency ◽  
Wave Guide ◽  
Transient Responses ◽  
Extremely Low Frequency ◽  
The Earth ◽  
Wave Forms

The paper is concerned with the connection between frequency domain and time domain for propagation in the earth–ionosphere wave guide. Attention is focussed on the extremely low frequency (e.l.f.) range. It is assumed that the propagation constant is proportional to (frequency)v where v is a fraction between 0 and 1. For such a frequency law, the corresponding transient responses are computed. These illustrate a number of important points. In particular, it is indicated that the frequency dependence of the propagation constant could be estimated directly from the wave forms themselves without resorting to conventional spectral analysis.

Subsurface radar propagation deconvolution

Geophysics ◽  
1994 ◽  
Vol 59 (2) ◽  
pp. 215-223 ◽  
Author(s):  
Greg Turner
Keyword(s):  
Frequency Dependence ◽  
Pulse Shape ◽  
Seismic Waves ◽  
Radar Data ◽  
Water Tank ◽  
Minimum Phase ◽  
The Earth ◽  
Q Model ◽  
Deconvolution Techniques ◽  
Amplitude Characteristics

The frequency dependence of attenuation is typically far greater for subsurface radar waves than for seismic waves. Since this frequency dependence causes the subsurface radar pulse shape to change as it propagates through the earth, conventional wavelet deconvolution techniques are often inadequate to reconstruct the earth’s reflectivity series. The application of a time‐variant filter that undoes the effect of frequency‐dependent attenuation can substantially improve the resolution of subsurface radar data. This filter is minimum‐phase with amplitude characteristics equal to the inverse of the attenuation function of the medium investigated. Preliminary tests on data from surveys over a water tank, an underground mine stope, and fractured granite suggest that good results can also be achieved by assuming attenuation is linearly proportional to frequency, similar to a constant Q model.

An estimate of the properties of Love-type surface waves in a frictionally bonded layer

1979 ◽  
Vol 69 (2) ◽  
pp. 305-317
Author(s):  
Richard K. Miller
Keyword(s):  
Experimental Data ◽  
Frequency Dependence ◽  
Surface Waves ◽  
Half Space ◽  
Elastic Layer ◽  
Coulomb Friction ◽  
Analytical Approach ◽  
Elastic Half Space ◽  
High Frequencies ◽  
The Earth

abstract An approximate analytical approach is presented for determining the attenuation, dispersion, and intensity of motion at depth associated with Love-type surface waves in an elastic layer bonded by Coulomb friction to an elastic half-space. It is found that the dispersion curves are only slightly affected by a small amount of slip at the interface, but that the level of attenuation in the system increases considerably with the amplitude of motion. The results for the frequency dependence of the attenuation in the system are in basic agreement with experimental data on the attenuation of Love waves in the Earth (Jackson, 1971). The results for the intensity of motion at depth indicate a deterioration of bonding at high frequencies.

Frequency Dependence of Radar Meteor Echo Rates

1986 ◽  
Vol 6 (3) ◽  
pp. 303-306 ◽  
Author(s):  
R. M . Thomas ◽  
P. S. Whitham ◽  
W. G. Elford
Keyword(s):  
Frequency Dependence ◽  
Fold Increase ◽  
Hf Radar ◽  
Visual Data ◽  
Missing Mass ◽  
Meteor Flux ◽  
The Earth ◽  
Mass Influx ◽  
Radar Meteor ◽  
Flux Incident

AbstractMeteor rates have been measured with a large HF Radar at a number of frequencies. At the top end of the HF band our results match those of Greenhow (1963). However at lower frequencies we find high echo rates which indicate that past observations measured only a few percent of the total meteor flux incident on the Earth’s atmosphere. This explains the ‘missing mass’ discrepancy observed when radar results are compared with satellite or visual data. Accounting for’this missing mass results in a four-fold increase in the calculated total meteoroid mass influx to the surface of the Earth from 4000 to 16,000 tonnes per year. Our results also imply that the majority of echoes originate from altitudes above 100 km.

The motion of a lunar orbiter

1966 ◽  
Vol 25 ◽  
pp. 373
Author(s):  
Y. Kozai
Keyword(s):  
Degrees Of Freedom ◽  
Dimensional Space ◽  
Artificial Satellite ◽  
Equations Of Motion ◽  
Triaxial Ellipsoid ◽  
The Moon ◽  
Secular Motion ◽  
The Earth ◽  
Close Satellite ◽  
The Mean

The motion of an artificial satellite around the Moon is much more complicated than that around the Earth, since the shape of the Moon is a triaxial ellipsoid and the effect of the Earth on the motion is very important even for a very close satellite.The differential equations of motion of the satellite are written in canonical form of three degrees of freedom with time depending Hamiltonian. By eliminating short-periodic terms depending on the mean longitude of the satellite and by assuming that the Earth is moving on the lunar equator, however, the equations are reduced to those of two degrees of freedom with an energy integral.Since the mean motion of the Earth around the Moon is more rapid than the secular motion of the argument of pericentre of the satellite by a factor of one order, the terms depending on the longitude of the Earth can be eliminated, and the degree of freedom is reduced to one.Then the motion can be discussed by drawing equi-energy curves in two-dimensional space. According to these figures satellites with high inclination have large possibilities of falling down to the lunar surface even if the initial eccentricities are very small.The principal properties of the motion are not changed even if plausible values ofJ3andJ4of the Moon are included.This paper has been published in Publ. astr. Soc.Japan15, 301, 1963.

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