Seismic methods have become common for the detection of low-throw faults ahead of underground coal mining. Surface
seismic methods cannot theoretically be used where dykes occur, because seismic waves transmit from the surface down to
the seams, and reflect back to the surface. Consequently, where sub-vertical structure such as dykes occurs, the surface
seismic method fails.
The ability of seismic methods to image dykes depends on the geometry used, the dyke thickness and the seismic wave
propagation mode in relation to dyke composition and internal structure. Surface seismic methods find it difficult to
distinguish between faults/fractures and very thin dykes (1-2m in thickness) when the dyke's thickness is less than the
seismic wavelength. Consequently, borehole seismic methods have to be used to detect the presence of such thin dykes.