UCLA

Microtremor-based horizontal-to-vertical spectral ratios (mHVSR) offer insights into subsurface seismic velocity structure, primarily through resonant features revealed by peaks in mHVSR curves. Typically derived from three-component broadband seismometers with high-pass corner frequencies of 0.0083 Hz over relatively short observation periods (1-2 hrs), mHVSR is a cost-effective and time-efficient method of site characterization. This approach has been shown to correlate with site-specific ground motion characteristics and recent studies suggest that mHVSR holds significant potential for improving ergodic ground motion models. This study produced mHVSR curves at 1,127 seismic stations with permanently installed broadband seismometers across California and neighboring states. Each mHVSR curve was uniformly processed using the Python library hvsrprocpy following standard procedures with minor modification. These data were added to the Community Shear-Wave Velocity (VS) Profile Database (VSPDB; https://vspdb.org) and are being used in ongoing work seeking to develop mHVSR-conditioned site terms in GMMs for California.