Stable inversion of measured VP and VS to estimate porosity in fluid-saturated soils

Porosity is an important state parameter which controls the response of porous materials under both static and dynamic loading. The possibility of determining porosity from direct inversion of V-P and V-S, which are routinely measured in geophysical prospecting, is appealing. A methodology has been recently proposed and successfully applied to a number of sites and it is based on the apparent insensitivity of porosity on Poisson ratio of the soil skeleton nu(SK), which is a priori an unknown quantity. So far, however, the functional dependence of porosity on nu(SK) has only marginally been investigated and doubts arise regarding whether the method is always applicable. This study attempts to investigate thoroughly the stability of the inversion of measured V-S and V-P to estimate porosity and to assess the degree of well-posedness of the procedure for all the combinations of V-P and V-S relevant in real soils.