Waveform inversion of crosshole data based on acoustic wave equation

Waveform inversion of crosshole data based on acoustic wave equation is investigated in this paper. The inversion is set as an optimization problem with the Lagrange multiplier function. The Tikhonov regularization is adopted in objective function. The gradient of the objective function is generated by solving the adjoint equation of the forward problem with the finite difference method. In order to prevent the quasi-Newton method to trap in local optimal value, a suitable initial model is required. For comparison, the traveltime inversion or tomography is implemented which provide smooth features of the velocity model. Numerical computations are given which show the good ability of the new velocity inversion method.