Abstract: A method is disclosed for determining improved estimates of properties of a model, on the basis of estimated prior constraints, by running a mathematical inversion several times using the output posterior estimate of the previous inversion, or any of the previous inversions to provide an input for the next inversion. This iterative inversion may be repeated until the prior and posterior estimates converge to within a given threshold. The method may be applied to seismic data, using a seismic inversion, in order to improve the prediction of the viability of potential petroleum reservoirs by determining improved estimates of volumetric properties of a subsurface region.