Microtremor Horizontal-to-Vertical Spectral Ratio (mHVSR) Data Collection at California Downhole Vertical Array Sites, 2022

The microtremor Horizontal-to-Vertical spectral ratio (mHVSR) method provides frequency-dependent ratios of Fourier amplitude spectra (FAS) for the horizontal to vertical components of a 3-component recording of ambient ground motions (typically velocities) from microtremors. This method can identify the frequencies associated with site resonances at sites with large impedance contrasts, and hence has potential to provide useful parameters for predicting seismic site response. The mHVSR method is applied by recording ground vibrations either from a temporarily-deployed seismometer, typically recording for a relatively short period of time (~1-2 hrs.), or from a permanently-installed broadband seismometer. It is also useful for studying the spatial, temporal, and azimuthal variation of ground vibrations at sites.

The overall goals of our HVSR research are to develop a publicly accessible database of HVSR data for use in research, to develop effective protocols for analysis and interpretation of HVSR data, and to develop methods for predicting site response conditioned on HVSR data. The database has been established and is available in the United States Community Shear-Wave Velocity (VS) Profile Database (PDB) (https://uclageo.com/VPDB/); the work presented in this doi is contributing to that database.