Stack of N layers

In section 4.2, the soil structure is modeled with a few layers of varying thicknesses. Alternatively, the velocity variation may be discretized by a great number of thin layers with fixed thicknesses. It is the usual technique for linearized inversion methods (Herrmann (1994)). It generally implies a greater number of parameters than the approach described in section 4.2.

In this section, we invert the same dispersion curve as in section 4.2. However, $V_p$ is supposed to be known in a deterministic way and without bias to allow the comparison of arbitrary and increasing profiles. In section 4.3.1, an additional inversion case is proposed with $V_p$ and $V_s$ as the variable parameters. The variation of velocity is represented by a stack of ten layers with fixed thicknesses (2, 3, 5, 8, 12, 17, 23, 30, 38, and 47 m) plus a half space. The density is fixed to 2 t/m$^3$ in all layers.