
%0 Journal Article
%A Soma, N. 
%A Utagawa, M. 
%A Seto, M. 
%A Asanuma, H. 
%T Application of the tri-axial drill-bit VSP method to drilling for geological survey in civil engineering
%J Exploration Geophysics
%D 2004/03/01
%V 35
%N 1
%P 70-79
%K 
%R https://doi.org/10.1071/EG04070
%U https://www.publish.csiro.au/paper/EG04070 
%X We have examined the applicability of the triaxial drill-bit VSP method (TAD-VSP) to the geological survey of possible sites for a high-level radioactive waste disposal repository. The seismic energy generated by a drill bit is measured by a downhole multi-component detector, and the resulting signals are processed to image the geological structure deep underground. In order to apply the TAD-VSP method to civil-engineering-scale drilling, we have developed a small but highly sensitive and precise three-component downhole seismic measurement system, and recorded drill-bit signals at a granite quarry. We have successfully imaged discontinuities in the granite, possibly related to fractures, as highly reflective zones. The discontinuities imaged by the TAD-VSP method correlate well with the results of other borehole observations. In conclusion, the TAD-VSP method is usable in geological investigations for civil engineering because the equipment is compact and it is simple to acquire the drill-bit signal. 
