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| | Abstract | | We have observed seismic signals from the small scale core-drilling at a small tunnel in hard rock mass, and evaluated the characteristic of the signals. The seismic energy from the small drilling was successfully detected in the observation well at a distance of 93 m. Good waveform often has near 20dB of signal-to-noise ratio in the range of 80-1100 Hz although average signal level is generally very low. Although the exact position of seismic emission is still unknown, 3D hodogram observation of the signals infers SV-wave mode. We have made a trial of reflection imaging using the drilling signals, and detected anomaly of high reflectivity under the tunnel. |
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