Imaging Near-surface Heterogeneities by Natural Migration of Back-scattered Surface Waves
A. AlTheyab, E. Workman, F.C. Lin and G.T. Schuster
Event name: 77th EAGE Conference and Exhibition - Workshops
Session: WS15 - Imaging, Characterization and Monitoring Using Interferometric Methods - Recent Developments
Publication date: 01 June 2015
Info: Extended abstract, PDF ( 1.14Mb )
Price: € 20
We present a surface-wave natural migration method that does not require velocity models to migrate backscattered surface waves to their projected locations on the surface. This method uses recorded Green's functions instead of simulated Green's functions. The key assumptions are that the scattering bodies are within the depth interrogated by the surface waves, and the Green's functions are recorded with dense receiver sampling. This natural migration takes into account all orders of multiples, mode conversions, and non-linear effects of surface waves in the data. The natural imaging formulas are derived for both active source and ambient-noise data, and computer simulations show that natural migration can effectively image near-surface heterogeneities with typical distributions of ambient-noise sources. We also present the results of applying natural migration to Long-Beach and US-Array passive data. The migration images highlight known discontinuities in surface-wave tomograms and correlate well with some of the prominent geological boundaries at two different scales: (1) the tectonic scale such as the edge of the Atlantic Plain Province in southeastern US and (2) the regional scale structure under Long Beach, California. The migration images provide complementary high-wavenumber information to the smoother surface-wave tomograms and can be used to refine the tomographic models.