Interferometry with a dense 3D dataset

In this paper we report on progress using ambient noise correlation with a dense 3D survey conducted in Long Beach, California, to estimate subsurface velocity. We show that both Rayleigh wave and body wave signals can be clearly observed between 0.2-10 Hz frequency range in the noise cross-correlations. The observed signals also compare well with an active source gather. We apply eikonal tomography to invert for the Rayleigh wave phase velocity maps at several different frequencies. The phase velocity maps, which are most sensitive to structure in the top 600 meters, show clear correlation with known surface features such as the slow anomaly adjacent to the coast in the south and a fast anomaly associated with the NewportInglewood fault zone. The results presented in this study show the potential of using ambient noise interferometry method to complement active source techniques in studying high-resolution shallow crustal structure.