Accounting for receiver perturbations in seismic wavefield gradiometry.

Spatial wavefield gradient data can be estimated from dense receiver arrays using a finite-difference approximation. Array-derived spatial wavefield gradient data to estimate, for example, strain and rotation components of the wavefield usually suffer from receiver perturbations, such as varying sensor coupling and/or differences in the instrument channel responses. We present a novel methodology to compute spatial seismic wavefield gradient data in the presence of receiver specific perturbation effects. We simultaneously invert the seismic wavefield recorded with an array consisting of closely spaced sensors for the spatial wavefield derivatives and station specific frequency-dependent calibration filters that remove the local receiver perturbations. Using synthetic and field data, we demonstrate that our scheme has the potential to significantly improve gradient estimation results for arrays with a low number of stations suitable, for instance, for land seismic exploration. The extracted calibration filters do not only correct for receiver perturbations but also partly compensate for the truncation error of the Taylor series expansion about the central (master) station of the array. The application of the calibration filters results in gradient estimates that are more accurate compared to conventional approaches. Multiple source recordings are used for reducing the trade-off between the extracted receiver perturbation filters and the spatial wavefield derivatives in the proposed inversion scheme. [ABSTRACT FROM AUTHOR]