Transmission tomography in a coal mine

A seismic survey was acquired in the coal mine of Monte Sinni near Carbonia, in the Sulcis region in SWSardinia, Italy. The survey was designed to verify the potentiality of seismic transmission tomography as a tool to map a-priori geometries and extension of the seam, and of the embedding rock, before they are excavated. In fact, notwithstanding the presence of detailed geologic sections along the galleries, it is not possible to predict the geometry and extension of the seam in the space between them. The tomographic experiment employed small charges and 3C receivers, placed along the galleries, so to illuminate a panel about 200 m wide and 800 m long between them. The validation of the results obtained through the tomographic inversion of the direct arrivals will be given once the panel will be excavated. However, it is possible to compare seismic velocity data with the geologic sections traced along the galleries. A good agreement is found between the negative velocity anomalies and the presence of the coal layers, and between the high velocity anomalies and the sterile intercalations.