Comparison of site dominant frequency from earthquake and microseismic data in California

An important predictive variable for site amplification is the site dominant frequency (⁠ƒ_d⁠). At seismic monitoring stations, ƒ_d can be calculated from the peak of the horizontal‐to‐vertical spectral ratios (HVSRs) obtained from earthquake recordings (eHVSR). For other sites, ƒ_d can be estimated from microseismic (mHVSR) observations. We compare the ƒ_d values derived from eHVSR (5% damped response spectra from the Next Generation Attenuation‐West2 [NGA‐West2] database; Ancheta et al., 2014) with those derived from mHVSR (Fourier spectra from Yong et al., 2013) for seismic stations in California. We show that the logarithm of eHVSR ƒ_d scales linearly with the logarithm of mHVSR ƒ_d⁠, with a standard deviation of 0.14log₁₀ units for mHVSR ƒ_d larger than 0.2 Hz. The relationship holds for microseismic surveys at distances up to 300 m away from the seismic stations. The results of this study have beneficial implications for the characterization of site response in modern ground‐motion models as well as in building codes.