Patent Document ID: 10036818
Application ID: 14330767
Patent Flag: 1

Claim One:
1. An iterative method for inverting measured geophysical data to infer a subsurface model of one or more physical properties, comprising: (a) using a subsurface property model, computing an objective function measuring misfit between model-simulated data and the measured geophysical data, wherein the model-simulated data are generated using a computer; (b) computing a gradient of the objective function with respect to parameters of the subsurface property model; (c) preconditioning the gradient by multiplying at least one vector by an approximation of a Hessian matrix, said Hessian matrix resulting from an operator of second derivatives with respect to parameters of the subsurface property model operating on the objective function, wherein the approximation of the Hessian matrix is a plurality of columns, but less than all, sampled from the Hessian matrix, and the approximation of the Hessian matrix is stored in a computer readable storage medium; (d) using the preconditioned gradient to update the subsurface property model; (e) repeating (a)-(d) at least once using the updated subsurface property model, wherein the approximation of the Hessian matrix is recomputed in some iterations of the steps (a)-(d) or in all iterations of steps (a)-(d); and (f) generating a subsurface image from a final updated subsurface property model from step (e) that was obtained with the approximation of the Hessian matrix, wherein the subsurface image identifies a location of structure in earth's subsurface that returned waves to receivers that recorded the geophysical data, and wherein (a)-(f) are implemented with a computer.