1887
  1. Home
  2. A-Z Publications
  3. Geophysical Prospecting
  4. Volume 40, Issue 6
  5. Article
Volume 40 Number 6
  • E-ISSN: 1365-2478

Abstract

A

The traditional method of exciting channel waves in coal deposits underground consists of firing explosive sources in a mid‐seam position generating seam waves of the Rayleigh and Love type. We investigate various source positions and excitation mechanisms within the bedrock structure surrounding the seam to evaluate the effects of source positions adjacent to the seam. The investigation is based on analogue and numerical modelling of half‐ and full‐space cases, for which the excitation and the nature of Rayleigh channel waves are examined.

In the analogue modelling, sources, located from mid‐seam out into the bedrock, along the edge of a 2D plate model, excited channel waves through a conversion of the free surface Rayleigh wave at the edge of the plate. The excited channel wave belongs to the normal mode range. Frequency‐wavenumber analysis shows that the symmetric 2nd mode of the channel wave is excited with frequencies comparable to the forcing frequency of the source signal. The polarization changes from retrograde to prograde, as the wave develops from the front to the rear of the seam, respectively. The amplitude‐depth distribution resembles that of an ordinarily excited seam wave, for the symmetric component. However, the antisymmetric component does not show the characteristic change of sign in amplitudes across the mid‐seam axis.

Numerical modelling with sources located in the bedrock (full‐space case) shows that relocating the source away from the seam lowers the frequency content of the excited channel wave. Based on these investigations, the influence of a lower‐frequency source signal on the excitation of the channel wave is examined in an analogue experiment. Sources are sited in the bedrock adjacent to the seam at three locations. A lower‐frequency wavelet is calculated for each source location from the results obtained in the numerical analysis. For comparison, a higher‐frequency wavelet is also used which is known to be optimal for this model geometry when excited by a mid‐seam source location. It is found that in two cases the use of the lower‐frequency wavelet improves the channel wave excitation, while no amplification is achieved in one case.

Loading

Article metrics loading...

/content/journals/10.1111/j.1365-2478.1992.tb00547.x
2006-04-27
2024-04-20

  • From This Site

    /content/journals/10.1111/j.1365-2478.1992.tb00547.x
    dcterms_title,dcterms_subject,pub_keyword
    -contentType:Journal -contentType:Contributor -contentType:Concept -contentType:Institution
    10
    5
Loading full text...

Full text loading...

References

  1. Albright, J.N. and Johnson, P.A.1990. Cross‐borehole observation of mode conversion from borehole Stoneley waves to channel waves at a coal layer. Geophysical Prospecting38, 607–620.
    [Google Scholar]
  2. Alekseev, A.S. and Mikhailenko, B.G.1978. The solution of dynamic problems of elastic wave propagation in inhomogeneous media by a combination of partical separation of variables and finite difference methods. Geophysics48, 161–172.
    [Google Scholar]
  3. Anderson, D.L.1961. Elastic wave propagation in layered anisotropic media. Journal of Geophysical Research66, 2953–2963.
    [Google Scholar]
  4. Behrens, J. and Waniek, L.1972. Modellseismik. Zeitschrift für Geophysik-Journal of Geophysics38, 1–44.
    [Google Scholar]
  5. Clayton, R. and Enquist, B.1977. Absorbing boundary conditions for acoustic and elastic wave propagation. Bulletin of the Seismological Society of America67, 1529–1540.
    [Google Scholar]
  6. Cochran, M.D., Woeber, A.F. and De Bremaecker, J.C.1970. Body waves as normal and leaking modes. Reviews of Geophysics and Space Physics8, 321–357.
    [Google Scholar]
  7. Dresen, L.1985. Flözwellenseismik für die untertägige Steinkohlenerkundung. In: Methoden der Angewandten Geophysik und Mathematische Verfahren in den Geowissenschaften. F.Bender (ed.), Band II, 261–298. Ferdinand Enke Verlag.
    [Google Scholar]
  8. Dresen, L. and Freystätter, S.1976. Rayleigh channel waves for the in‐seam seismic detection of discontinuities. Journal of Geophysics42, 111–129.
    [Google Scholar]
  9. Franssens, G.R., Lagasse, P.E. and Mason, I.M.1985. Study of leaking channel modes of in‐seam exploration seismology by means of synthetic seismograms. Geophysics50, 414–424.
    [Google Scholar]
  10. Freystätter, S. and Dresen, L.1977. Ausbreitung von Rayleigh–Kanalwellen in Steinkohlenflözen – Modellseismische Untersuchungen. Journal of Geophysics43, 807–828.
    [Google Scholar]
  11. Freystätter, S. and Dresen, L.1978. The influence of oblique dipping discontinuities on the use of Rayleigh channel waves for the in‐seam seismic reflection method. Geophysical Prospecting26, 1–15.
    [Google Scholar]
  12. Haskell, N.A.1953. The dispersion of surface waves on multilayered media. Bulletin of the Seismological Society of America43, 17–34.
    [Google Scholar]
  13. Kerner, C.1984. Untersuchungen an zweidimensionalen analogen und numerischen Modellen zur Transmission und Reflexion von Love‐ und Rayleigh‐Flözwellen. Berichte des Instituts für Geophysik der Ruhr‐Universität Bochum, Reihe A, Nr. 14.
  14. Kerner, C. and Dresen, L.1985. The influence of dirt bands and faults on the propagation of Love seam waves. Journal of Geophysics57, 77–89.
    [Google Scholar]
  15. Kodera, K., De Villedary, C. and Gendrin, R.1976. A new method for the numerical analysis of non‐stationary signals. Physics of the Earth and Planetary Interiors12, 142–150.
    [Google Scholar]
  16. Krollpfeifer, D.1989. Zielgerichtetes Anschießen ausgewählter Untergrundstrukturen mit P‐ und S‐Wellen. In: Beiträge zur Minderung des Explorationsrisikos. 9. Mintrop‐Seminar. W. Budach, L. Dresen, J. Fertig and H.Rüter (eds). DGMK/Unikontakt, Ruhr‐Universität Bochum9, 87–129.
    [Google Scholar]
  17. Küpper, F.1958. Theoretische Untersuchungen über die Mehrfachaufstellung von Geophonen. Geophysical Prospecting6, 194–256.
    [Google Scholar]
  18. March, D.W. and Bailey, A.D.1983. A review of the two‐dimensional transform and its use in seismic processing. First Break1(1), 9–21.
    [Google Scholar]
  19. Meister, J. and Dresen, L.1987. Hybrid seismic modelling: A technique to combine physical and computer methods for vertical wave incidence. Geophysical Prospecting35, 815–831.
    [Google Scholar]
  20. O'Brien, P.N.S. and Symes, M.P.1971. Model seismology. Reports on Progress in Physics34, 697–764.
    [Google Scholar]
  21. Phinney, R.A.1961. Leaking modes in the crustal wave guide. Journal of Geophysical Research66, 1445–1469.
    [Google Scholar]
  22. Radovich, B.J. and De Bremaecker, J.C.1974. Body waves as normal and leaking modes –leaking modes of Love waves. Bulletin of the Seismological Society of America64, 301–306.
    [Google Scholar]
  23. Sheriff, R.E. and Geldart, L.P.1985. Exploration Seismology. Vol. 2: Data Processing and Interpretation. Cambridge University Press.
    [Google Scholar]
  24. Watson, T.H.1972. A real frequency, complex wavenumber analysis of leaking modes. Bulletin of the Seismological Society of America62, 369–384.
    [Google Scholar]
http://instance.metastore.ingenta.com/content/journals/10.1111/j.1365-2478.1992.tb00547.x
Loading
  • Article Type: Research Article

Most Cited This Month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error