Dispersion curves and small-scale geophysics using noise cross-correlation techniques

Abstract

It has been demonstrated, both theoretically and experimentally, that the Green’s function between two receivers can be retrieved from cross-correlation of isotropic noise records. Since surface waves dominate noise records in geophysics, tomographic inversion using noise correlation techniques have been performed from Rayleigh waves so far. However, very few numerical studies implying surface waves have been conducted to confirm the extraction of the true dispersion curves from noise correlation in a complicated sedimentary ground model. In this work, synthetic noise has been generated in a small-scale (<1 km) numerical realistic environment and classical processing techniques are applied to retrieve the phase velocity dispersion curves in the medium, first step toward an inversion. We compare results obtained from SPAC (spatial auto-correlation method) and noise correlation techniques on a ten-element array. Two cases are presented in the (1–20 Hz) frequency bandwidth that corresponds to an isotropic or a directional wavefield noise.