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Swiss Journal of Geosciences
Fig. 9 | Swiss Journal of Geosciences

Fig. 9

From: A laboratory approach for the calibration of seismic data in the western part of the Swiss Molasse Basin: the case history of well Humilly-2 (France) in the Geneva area

Fig. 9

Example of seismic velocity anisotropy and Poisson’s ratio as a function of confining pressure up to 300 MPa. The curves are inter- and extrapolated from laboratory measurements using the equation of Wepfer and Christensen (1991). The plot is split into two areas, on the basis of the linearity of the curves. The low-pressure zone, where the curves are non-linear, represents the pressure interval where the seismic behavior is dominating by crack and pore closures (e.g., Birch 1960). It shows an abrupt decrease due to the closure of the aligned microcracks which reinforce the anisotropy induced by the lattice-preferred orientation (LPO) of anisotropic minerals (sample: HU24). Above 150 MPa, the curves become linear; the elastic behavior of the rocks is determined by the elastic moduli of the rock-forming minerals

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