Abstract
AbstractThe dynamic finite‐element method allows frequency‐dependent reflection and transmission coefficients to be computed for Love waves scattered by two‐dimensional inhomogeneities in coal seams.Clean faults of zero hade angle show a throw‐dependent cross‐over frequency in reflection spectra, and throw‐dependent conversion from fundamental to first higher mode energy in transmission spectra. Oblique faults show mode conversion in reflection spectra which is relatable to the fault hade angle by simple Huygens‐theory models. Thin fracture zones or dykes normal to the seam show a reflection maximum when thickness of the zone is of order one quarter of the seam wave wavelength.Published field data from two known faults and a dyke are compared with the modeling results and support the belief that broad‐band seam‐wave data are capable of characterizing a seam discontinuity (throw, hade angle, dyke thickness) as well as locating it. Development of such procedures will require extensions to existing field practice and processing.This research was funded in part by the National Energy Research Development and Demonstration Council of Australia. The authors thank The Broken Hill Proprietary Company Limited for permission to quote from company case histories.
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