38 Well seismic surveying and acoustic logging a b Figure 1.24 Crosshole examples; a: left, S recordings between 22 and 29 m in depth and, right, associated geological model; b: P and S time-distance curve, with a measurement level at 2 m from the interface with a faster strata (based on the bottom right model). The above approach requires time and experience. It is therefore difficult to generalize to apply to all applications. The ASTM standard recommends the implementation of a computer analysis to take into account the different possible paths (inversion). In practice, this was not carried out in France, but has started to be used since 2015. Figure 1.25 shows an example of tomography results obtained with inversion software.
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