Transmission characteristics of in-seam seismic waves through dykes at German Creek Central Colliery, Queensland

Abstract

An in-seam seismic survey was conducted by the Australian Coal Industry Research Laboratories (ACIRL) at the German Creek Central Colliery, Queensland, to detect and delineate dykes obstructing mining operations within the coal seam. A transmission analysis of the Love and Rayleigh waves has been carried out to test for absorption of the seismic energy by the dykes and hence to determine the viability of identifying the dykes using this technique. The seismograms and amplitude spectra for these wave types indicated significant attenuation across the survey area which included the three dykes. Finite difference and finite element modelling of the dykes was used to predict the absorption properties of the dykes. A study of the transmission losses in both the field and model data revealed that in-seam seismic data required coherent signals at frequencies greater than 250 Hz for detecting dykes in a coal seam of 2.5 m thickness.