Authors: Lynch, RA


DOI https://doi.org/10.36487/ACG_rep/1201_14_lynch

Cite As:
Lynch, RA 2012, 'Active seismic monitoring', in Y Potvin (ed.), Deep Mining 2012: Proceedings of the Sixth International Seminar on Deep and High Stress Mining, Australian Centre for Geomechanics, Perth, pp. 201-210, https://doi.org/10.36487/ACG_rep/1201_14_lynch

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Abstract:
The use of controlled sources of seismic radiation can facilitate a better understanding of the rock mass response to mining. Ideally, the seismic sources should be highly repeatable so that differences in seismic transmission over time can be more easily studied and related to mining. Field trials of such a seismic source at El Teniente Mine (Chile) and Mponeng Mine (South Africa) have shown that massive stacking can be used to provide useful signal-to-noise ratios despite normal mining noises, on hourly time scales. The maximum range tested here is 200 m between source and receiver, using a 5 hour data set. Seismic velocity variations can be estimated on an hourly basis, to an accuracy of not less than 10-4. The technique appears sensitive enough to detect changes in stress caused by blasting 100 m away from the source-sensor ray. Significant S-wave radiation has also been recorded from the isotropic seismic source, and is most likely the result of P-S conversion at the borehole wall. The limitations of analogue cable length between source and sensor, as well as the awkwardly large datasets, have been overcome by an automatic pre-stacking algorithm within the seismic station, as demonstrated at Ridgeway mine (Australia). Pre-stacking reduces the amount of recorded data by a factor 300, to about 80 MB/sensor/day.

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