Patent ID: 8576661

Claim:
A method for investigating material surrounding a borehole, the method comprising: generating a first lower frequency acoustic wave within the borehole, wherein the first lower frequency acoustic wave induces a linear distortion in one or more features of inhomogeneities in the material surrounding the borehole and a nonlinear distortion in one or more features of inhomogeneities in the material surrounding the borehole that are substantially perpendicular to a radius of the borehole; directing a first sequence of higher frequency pulses in a direction perpendicular with respect to the longitudinal axis of the borehole into the material contemporaneously with the first acoustic wave; and receiving at one or more receivers positionable in the borehole one or more second higher frequency pulses produced by an interaction between the first sequence of higher frequency pulses and the one or more features of inhomogeneities in the material that are undergoing the linear distortion and the nonlinear distortion due to the first lower frequency acoustic wave.