This study presents a method for high-resolution surface wave tomography using ambient seismic noise. By cross-correlating one month of ambient seismic noise recorded at USArray stations in California, hundreds of short-period surface-wave group-speed measurements were obtained. These measurements were used to construct tomographic images of the principal geological units beneath California, revealing low-speed anomalies corresponding to sedimentary basins and high-speed anomalies corresponding to igneous cores of major mountain ranges. This method improves the resolution and fidelity of crustal images obtained from surface wave analyses. The method uses ambient seismic noise, which is random and isotropic, to extract surface wave dispersion data. This approach overcomes the limitations of traditional earthquake-based methods, which are limited by the spatial extent and frequency content of seismic waves. The key idea is that cross-correlation of ambient noise produces waveforms similar to the Green function between receivers, allowing the extraction of Rayleigh wave Green functions from ambient noise. The study used 30 days of continuous data from 62 USArray stations in California to estimate short-period surface wave dispersion curves. Tomographic inversion was applied to these data to produce group speed maps across California. The maps showed significant variance reductions, indicating improved resolution of crustal structures. Geological features such as sedimentary basins, igneous cores, and active faults were clearly identified in the maps. The results demonstrate that ambient seismic noise can provide detailed information about the shallow and middle crust. This method is particularly useful for temporary seismic arrays, as it can provide useful information even when earthquakes are not present. The method enhances resolution by using regularly spaced receivers, which may be much closer to each other than to earthquakes. The study also highlights that ambient noise can be a reliable and economical alternative to active seismic sources for seismic observations.This study presents a method for high-resolution surface wave tomography using ambient seismic noise. By cross-correlating one month of ambient seismic noise recorded at USArray stations in California, hundreds of short-period surface-wave group-speed measurements were obtained. These measurements were used to construct tomographic images of the principal geological units beneath California, revealing low-speed anomalies corresponding to sedimentary basins and high-speed anomalies corresponding to igneous cores of major mountain ranges. This method improves the resolution and fidelity of crustal images obtained from surface wave analyses. The method uses ambient seismic noise, which is random and isotropic, to extract surface wave dispersion data. This approach overcomes the limitations of traditional earthquake-based methods, which are limited by the spatial extent and frequency content of seismic waves. The key idea is that cross-correlation of ambient noise produces waveforms similar to the Green function between receivers, allowing the extraction of Rayleigh wave Green functions from ambient noise. The study used 30 days of continuous data from 62 USArray stations in California to estimate short-period surface wave dispersion curves. Tomographic inversion was applied to these data to produce group speed maps across California. The maps showed significant variance reductions, indicating improved resolution of crustal structures. Geological features such as sedimentary basins, igneous cores, and active faults were clearly identified in the maps. The results demonstrate that ambient seismic noise can provide detailed information about the shallow and middle crust. This method is particularly useful for temporary seismic arrays, as it can provide useful information even when earthquakes are not present. The method enhances resolution by using regularly spaced receivers, which may be much closer to each other than to earthquakes. The study also highlights that ambient noise can be a reliable and economical alternative to active seismic sources for seismic observations.