Estimating location of scatterers using seismic interferometry of scattered rayleigh waves

From non-destructive testing to medical imaging and seismology, estimating the location of scatterers is of high importance. The location estimation can be achieved using a method inspired by seismic interferometry. This method correlates only the isolated scattered fields from a scatterer, and inverts for the travel times to estimate the scatterer's location. The correlation eliminates the influence of the path between a source and a scatterer. We illustrate the potential of the method using data from a scaled laboratory model, representing geophysical field problems. We use ultrasonic data recorded on an aluminum block containing many scatterers at the surface represented by vertical drill holes. To estimate the horizontal coordinates of a scatterer, we use the scattered Rayleigh-wave fields recorded along two lines due to one source. We address the problem of selecting scattered fields along the two lines that pertain to the same scatterer using simple geometrical considerations, but also during the inversion. We show that the inversion does not converge when scattered fields coming from different scatterers have been chosen for the correlation.