33 1. Shear velocity measurement in boreholes Figure 1.18 Illustration of a 3 borehole crosshole system. Figure 1.19 Illustration of a P source: sparker (SolGéo). Moreover, having a single receiver borehole can be disadvantageous if we want to pick the first arrival time at the maximum wave amplitude (apex), rather than at its beginning. Admittedly, this technique makes it possible to work with signals with a signal-to-noise ratio that is not so good. Moreover, due to the signal attenuation,
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