<i>P-SV</i> wave scattering by coal‐seam inhomogeneities

Edwards, Suzan; Asten, Michael; Drake, Lawrence A.

doi:10.1190/1.1441911

Cited by 17 publications

(18 citation statements)

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“…interference pattern is still evident, in agreement with the investigations of Edwards et al (1985) on the Rayleigh wave transmission and reflection spectra for stone roll models. The high-frequency spectral amplitudes of the reflectivity curves increase by the same factor as the normalized maximum displacement amplitudes with increasing degree of erosion.…”

Section: Seam Thinning-variation Of the Degree Of Erosionsupporting

confidence: 88%

“…The high-frequency spectral amplitudes of the reflectivity curves are merely diminished by the same factor as the maximum displacement amplitudes of the reflected Love seam-waves with decreasing dip of the discontinuities. The interference maxima and minima become less evident, in agreement with investigations by Edwards et al (1985) on the Rayleigh wave transmission and reflection spectra for a dipping dike.…”

Section: Seam Interruption-variation Of the Dip Angle Of The Discontisupporting

confidence: 87%

“…They found a maximum in the first mode Love wave reflection spectrum if the quarter wavelength coincides with the extension of the fracture zone, in agreement with the first order constructive interference condition for thin layers. Edwards et al (1985) confirmed the interferences for Rayleigh waves of the first symmetric mode, too, evaluating the reflection and transmission spectra for vertical dikes.…”

Section: Seam-interruption Variation Of the Horizontal Oflsetsupporting

confidence: 68%

“…Since they assumed a velocity reduction in the fracture zone these models are comparable to those of a seam interruption. Edwards, Asten and Drake (1985) investigated dikes of 90" and 60" dip and stone rolls of two-thirds seam thickness length. The dikes cause seam interruptions of one seam thickness length or less.…”

Section: Introductionmentioning

confidence: 99%

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Love‐type Seam‐waves in Washout Models of Coal Seams*

Breitzke

Dresen

1986

Geophysical Prospecting

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The propagation of Love seam-waves across washouts of coal seams was studied by calculating synthetic seismograms with a finite-difference method. Seam interruption, seam end and seam thinning models were investigated. The horizontal offset, the dip of the discontinuities and the degree of erosion served as variable parameters. Maximum displacement amplitudes, relative spectral amplitudes and phase and group slowness curves were extracted from the synthetic seismograms.Both seam interruption and seam thinning reduce the maximum displacement amplitudes of the transmitted Love seam-waves. The degree of amplitude reduction depends on the horizontal offset and the degree of erosion. It is four times greater for a total seam interruption than for an equivalent seam thinning with a horizontal offset of four times the seam thickness. In a seam cut vertically, the impedance contrast between the coal and the washout filling determines the maximum displacement amplitudes of the reflected Love seam-waves. They diminish by a maximum factor of four in oblique interruption zone discontinuities with a dip of maximum 27", and by a maximum factor of ten in a seam thinning with a degree of erosion of at least 22%.The analysis of the relative spectral amplitudes indicates a preferential transmission of those phases with frequencies below, and a preferential reflection of those phases with frequencies above the first mode Airy-phase. The relative spectral amplitudes of the reflected Love seam-waves show a distinct interference pattern of the waves reflected at both interruption zone discontinuities.The dispersion analysis reveals a flattening of the phase and group slowness curves with increasing frequencies, horizontal offset and degrees of erosion.These results imply that a detection of washouts in-mine will be possible in a frequency range including at least the first mode Airy-phase. An interference pattern and a flattening of the dispersion curve indicate a washout rather than other seam obstructions and leads to an estimate of the washout dimension.

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Section: Seam Thinning-variation Of the Degree Of Erosionsupporting

confidence: 88%

Section: Seam Interruption-variation Of the Dip Angle Of The Discontisupporting

confidence: 87%

Section: Seam-interruption Variation Of the Horizontal Oflsetsupporting

confidence: 68%

Section: Introductionmentioning

confidence: 99%

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Love‐type Seam‐waves in Washout Models of Coal Seams*

Breitzke

Dresen

1986

Geophysical Prospecting

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“…Reflection and transmission coefficients have been obtained by other authors using physical models Freystatter 1976, Freystatter andDresen 1978), finite differences (Korn and Stockl 1982), and finite elements (Asten et al 1984, Edwards et al 1985. The physical models are restricted to P-SV channel wave studies because of the difficulty associated with studying SH-waves with such models.…”

Section: Results F O R V a R I O U S F A U L T Configurationsmentioning

confidence: 99%

The Scattering of Sh‐channel Waves by a Fault in a Coal Seam*

Buchanan¹

1986

Geophysical Prospecting

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BUCHANAN, D.J. 1986, The Scattering of SH-Channel Waves by a Fault in a Coal Seam, Geophysical Prospecting 34,343-365.The imaging of faults in coal seams by the in-seam seismic method has now become standard practice. In the UK over 300 surveys have been undertaken and the technique is now part of the exploration arsenal of colliery planners. From these users comes the pressure for two major improvements, namely an increase in range and target identification. This paper is directed towards the latter problem.It has long been recognized that the reflected channel waves must contain information on the fault structure that caused the reflection, and model experiments have been undertaken to investigate the reflection process. Only recently, however, have attempts been made to quantify the reflection process. Calculations using both the finite-difference and finiteelement techniques have been carried out, and estimates of the reflection coefficient as a function of frequency have been obtained. The object of this paper is to extend these considerations by calculating analytically the scattering matrix of an SH-channel wave after interaction at a fault plane. The scattering matrix is calculated as a function of frequency, hade angle, and fault throw.The method employed is based on the decomposition of the incident SH-channel wave into Fourier components, the calculation of plane wave reflection and transmission coefficients within the constraints of geometrical acoustics, and finally the synthesis of the scattering matrix by application of the Helmholtz-Kirchhoff integral. The calculation throughout is restricted to normal modes.

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Coal seam mapping by underground in-seam seismic surveys

Hatherly

1987

Geoexploration

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P-SV wave scattering by coal‐seam inhomogeneities

Cited by 17 publications

References 0 publications

Love‐type Seam‐waves in Washout Models of Coal Seams*

Love‐type Seam‐waves in Washout Models of Coal Seams*

The Scattering of Sh‐channel Waves by a Fault in a Coal Seam*

Coal seam mapping by underground in-seam seismic surveys

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