The present computational approach using the theory of diffuse field concept for earthquake (DFCe) is introduced to retrieve the subsurface velocity structures at the whole K-NET and KiK-net stations and to estimate the associated uncertainties. Remarkable agreement could be achieved between the identified velocities retrieved from DFCe and those obtained from in-situ PS loggings. The effective bedrock depth (����) is assumed to correlate with the fundamental peak frequency (�0) based on a proposed quarter wavelength approach. The ���� must be larger than its corresponding wavelength (�) and have the minimum difference (����−�). The newly established frequency-depth regression needs to be defined as a function of the average S-wave velocity overlying the ����. The �0 has correlation trends with the depths to the layers, where S-wave velocities ≥ 800 m/s and ≥ 3000 m/s. The outliers in these correlation trends exist because of unsatisfying the condition of the ����