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Seismic Velocities Measured in a Mine tunnel at Thabazimbi, South Africa
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 6th SAGA Biennial Conference and Exhibition, Sep 1999, cp-221-00014
Abstract
Analysis of the refracted arrivals on a seismic reflection profile recorded along the wall of a<br>tunnel al an iron mine near Thabazimbi, South Africa, shows significant variation in P-wave<br>velocity in dolomite in and away from the de-stressed zone. Very low seismic velocities away<br>from the tunnel wall are associated with alcoves or ‘cubbies' involving offsets in the wall of up<br>to 10 m. Large variations in seismic velocity resolved over distances less than 15 m with<br>signals of wavelength around 6-9 m are attributed to variations in the fracture systems in the<br>de-stressed zone. The results show that refraction static processing of ‘in-mine’ seismic<br>reflection profiles is as important as in surface surveys, since the frequency content of deep<br>mine seismic energy is higher than on surface, and can assist in analysis of stress regimes<br>within in-mine developments.