Poster Presentation

In this study, we use ambient noise data recorded at stations of the Southern California Seismic Network and three dense petroleum industry surveys to show the occurrence of surface wave mode interference and prove that, if not properly accounted for, it can affect the accuracy of phase and group velocity measurements. We then present a mode-modeling approach that allows us to jointly measure the phase velocities of the fundamental mode and higher mode Rayleigh waves despite them having partially overlapping group arrival times. We demonstrate the reliability of our method by constructing frequency-dependent phase velocity maps of the fundamental mode and first overtone surface waves beneath the seismic arrays. The tomographic reconstructions provide a clear and interpretable image of the sub-surface velocity distribution and show a strong correlation with known geologic structures such as the Newport Inglewood Fault system. Although the technique presented here is only applied for the fundamental mode and first overtone Rayleigh waves, our approach can be easily expanded to higher-order modes and promises to be a reliable way to characterize high-frequency surface waves at unprecedented resolutions.