Three-dimensional shear wave velocity imaging by ambient seismic noise tomography

3-D shear wave velocity images are of particular interest for engineering seismology. To obtain information about the local subsoil structure, we present a one-step inversion procedure based on the computation of high-frequency correlation functions between stations of a small-scale array deployed for recording ambient seismic noise. The calculation of Rayleigh wave phase velocities is based on the frequency-domain SPatial AutoCorrelation technique. Constitutively, a tomographic inversion of the traveltimes estimated for each frequency is performed, allowing the laterally varying 3-D surface wave velocity structure below the array to be retrieved. We test our technique by using simulations of seismic noise for a simple realistic site and by using real-world recordings from a small-scale array performed at the Nauen test site (Germany). The results imply that the cross-sections from passive seismic interferometry provide a clear image of the local structural heterogeneities and the shear wave velocities are satisfactorily reproduced. The velocity structure is also found to be in good agreement with the results of geoelectrical measurements, indicating the potential of the method to be easily applied for deriving the shallow 3-D velocity structure in urban areas and for monitoring purposes.