Illuminating Subsurface Structures Beneath Lake George Fault Zone, Southeast Australia with Traffic Noise

Abstract Mapping fault-zone properties is crucial for mitigating seismic hazards, particularly in urban settings. This process often requires high-resolution seismic imaging, which depends on dense data coverage and high-frequency seismic energy sensitive to shallow structures, with traffic noise providing an ideal source. However, extracting coherent phases from traffic noise remains challenging due to the complex conditions of variable sources and array configurations. Although array seismology techniques enhance coherence, they can limit model resolution. In this study, we demonstrate that high-quality surface Rayleigh-wave dispersions (2.5–10 Hz) can be extracted from single-station-pair cross correlations using a meticulously designed dense nodal array near a highway in the Lake George fault zone, southeast Australia. By analyzing the complete nine-component cross-correlation tensor, we find that radial–radial correlations, rather than conventional vertical–vertical correlations, yield the strongest dispersion signals. These high-frequency dispersion measurements enable surface-wave tomography, providing the first detailed velocity structure of the top 800 m of the fault zone. The mapped Lake George fault zone displays seismic characteristics similar to those of several major active fault systems worldwide. It represents a long-lived damage zone capable of hosting significant seismic events. These results provide new insights into the application of traffic noise for near-surface imaging and monitoring in urban environments, and they have significant implications for considering the directionality of distributed acoustic sensing data in future work.