Patent ID: 8750074

Claim:
A method of evaluating an earth formation, the method comprising: deploying a plurality of seismic receivers in a borehole and receiving seismic signals in the plurality of seismic receivers responsive to an activation of at least one seismic source at a plurality of positions on the surface of the earth; using at least one processor configured to estimate, from travel times of the received seismic signals, a velocity model including velocities of vertically propagating seismic waves in a plurality of intervals, and at least two anisotropy parameters related to a normal moveout curve of compressional waves for the plurality of intervals, wherein at least one of the two anisotropy parameters is a Thomsen parameter ε, the Thomsen parameter ε being estimated using a fraction set to a value between 0 and 0.5, the fraction comprising a square of a ratio of a shear velocity to a compressional wave velocity divided by a result of one minus the square of the ratio of the shear velocity to the compressional wave velocity; and using the estimated velocity model for producing an image of the earth formation.