Patent ID: 8812282

Claim:
A computer-implemented method for inversion of measured geophysical data to determine a physical properties model for a subsurface region, comprising: (a) obtaining a group of two or more encoded gathers of the measured geophysical data, wherein each gather is associated with a single generalized source or, using source-receiver reciprocity, with a single receiver, and wherein each gather is encoded with a different encoding function selected from a set of non-equivalent encoding functions; (b) summing the encoded gathers in the group by summing all data records in each gather that correspond to a single receiver, or source if reciprocity is used, and repeating for each different receiver, resulting in a simultaneous encoded gather; (c) assuming a physical properties model of the subsurface region, said model providing values of at least one physical property at locations throughout the subsurface region; (d) inverting, using a computer, the measured geophysical data, one simultaneous encoded gather at a time, using the assumed physical properties model as an initial model, and iteratively updating said model to minimize a cost function measuring degree of misfit between model-simulated data and the measured geophysical data to generate an updated physical properties model, wherein the model-simulated data are generated in a simulation that comprises solving a wave propagation equation, and wherein model adjustments are made in the updating using a gradient of the cost function with respect to at least one model parameter, which gradient is computed from a time integration of a product of encoded simultaneous-source data simulated forward in time and encoded simultaneous-source data simulated backward in time; and (e) downloading the updated physical properties model or saving it to computer storage.