The authors present a novel method for high-resolution surface wave tomography using ambient seismic noise recorded at USArray stations in California. By cross-correlating ambient noise, they obtain short-period surface wave group-speed measurements, which are then used to construct tomographic images of the geological units beneath California. The method reveals low-speed anomalies in sedimentary basins and high-speed anomalies in igneous cores of mountain ranges. This approach enhances the resolution and fidelity of crustal images compared to traditional methods based on earthquake-generated waves, which are limited by attenuation, scattering, and the spatial extent of surface wave sensitivity. The method is particularly advantageous for temporary seismic arrays, as it can provide useful information even when no earthquakes occur. The results demonstrate that ambient seismic noise can yield deterministic information about the Earth's crust, highlighting its potential as a reliable and economical alternative to traditional seismic probing methods.The authors present a novel method for high-resolution surface wave tomography using ambient seismic noise recorded at USArray stations in California. By cross-correlating ambient noise, they obtain short-period surface wave group-speed measurements, which are then used to construct tomographic images of the geological units beneath California. The method reveals low-speed anomalies in sedimentary basins and high-speed anomalies in igneous cores of mountain ranges. This approach enhances the resolution and fidelity of crustal images compared to traditional methods based on earthquake-generated waves, which are limited by attenuation, scattering, and the spatial extent of surface wave sensitivity. The method is particularly advantageous for temporary seismic arrays, as it can provide useful information even when no earthquakes occur. The results demonstrate that ambient seismic noise can yield deterministic information about the Earth's crust, highlighting its potential as a reliable and economical alternative to traditional seismic probing methods.