Double beamforming processing in a seismic prospecting context

Abstract

The use of larger numbers of sensors is becoming more common at the large, continental scale for deep-structure imaging in seismology, and at a smaller scale with exploration geophysics objectives. Seismic arrays require array processing from which new types of observables contribute to a better understanding of the wave propagation complexity. From among these array processing techniques, this study focuses on a way to select and identify different phases between two source-receiver arrays based on the double beamforming (DBF) method. At the exploration geophysics scale, the goal is to identify and separate low-amplitude body waves from high-amplitude dispersive surface waves. A synthetic data set from a finite-difference time-domain simulation is first used to validate the array processing method. From directional information obtained with DBF, and due to the double-plane wave projection, it is demonstrated that surface and body waves can be extracted with a higher efficacy compared to classical beamforming even at short offset. A seismic prospecting data set in a laterally heterogeneous medium is then investigated. This data set is a high-resolution survey which provides a perfect control on source and receiver arrays geometry. The separation between the direct surface and body waves is observed after DBF and ray bending is discussed from the additional azimuthal information.