Inversion of surface wave dispersion and reflectivity imaging using ambient noise seismic interferometry

Abstract

Seismic exploration typically measures signals originating from a carefully constructed seismic source. If the same results can be accomplished without requiring a man-made source, but rather relying on randomly distributed ambient noise signals, significant cost reductions are possible. The main goal of this research is to efficiently retrieve near-surface shear wave velocity profiles from ambient seismic noise. Shear wave velocities allow for computation of rock properties that are key factors in e.g. building-construction as well as in mining, drilling and reservoir production activities. A line of seismic receivers was set up near ‘De Grote Peel’ national park in the Netherlands, which recorded ambient seismic noise over a period of 35 days. Surface wave signals are extracted from passive seismic data through the process of ‘ambient noise seismic interferometry’ (ANSI). This involves cross-correlating the signal responses recorded with a line of receivers in order to make virtual source gathers. Surface wave components with different wavelengths will travel at different speeds and disperse. Dispersion curves are generated from the surface waves and inverted using a neighborhood algorithm. The resulting shear wave velocity profiles are successfully linked to formation transition depths from borehole data. As a side-project, zero-offset autocorrelations are used to image deep reflecting layers. The resulting reflectors are successfully linked to vintage active seismic data. This research has been successful in finding efficient methods for imaging both deep reflecting layers and near-surface shear wave velocity profiles, solely from ambient seismic noise recordings.