1. A computer-implemented method for joint inversion of two or more sets of geophysical data of different types, measured in surveys of a subsurface region, to obtain a model of at least one geological property for the subsurface region, said method comprising: using a computer to jointly invert the sets of geophysical data, using structural coupling between the different data types, to obtain models of geophysical properties corresponding to the sets of geophysical data, said structural coupling being determined from the geophysical data or from a priori knowledge of the subsurface region; partitioning the subsurface region into sub-regions based on similar combinations of geophysical parameters in the geophysical property models that correlate to particular lithologies, thereby defining lithology sub-regions; determining mathematical rock physics relationships appropriate for each lithology, said rock physics relationships relating geological properties to geophysical properties; and using a computer to jointly invert the sets of geophysical data, using the rock physics relationships according to lithology sub-region, to obtain a model of one or more of the geological properties for the subsurface region, wherein at least one of the sets of geophysical data are filtered using a low-pass filter before the jointly inverting with structural coupling, which inverting uses a computational grid with coarseness of scale consistent with frequency content passed by the low-pass filter.