Acoustic wave-equation based full-waveform microseismic source location using improved scattering-integral approach

Abstract

A novel acoustic wave-equation-based full-waveform source location method is proposed to locate microseismic sources accurately and efficiently. The proposed Fréchet derivatives of waveform with respect to location parameters are in two parts, one of which accounts for the influence of geometrical perturbation, the other accounts for the influence of spatial velocity variation on source location. Sources are accurately located with the new formula, especially in complex velocity models. The proposed method uses an improved scattering-integral (SI) approach which efficiently locates the source and almost halves the usual computation cost. To further accelerate the locating procedure, the truncated Gauss–Newton method is applied at negligible extra computation cost. Numerical tests show that far fewer iterations are needed for source location using this method than with the more commonly used conjugate gradient method. To reduce the problem of cycle skipping, correlation is applied to select the best starting source positions. Both 2-D and 3-D numerical examples are presented to demonstrate the validity and high efficiency of the proposed method, and the robustness of the proposed method is also tested for the case when the velocity model is inaccurate or the signal to noise ratio is low. Finally, field data are used to show the realistic performance of the proposed method.