Characterizing Fundamental Frequencies Across Geologies Using Ambient Noise HVSR

Rileigh Mansfield, Sajan K C, & Chukwuebuka C. Nweke

Submitted September 7, 2025, SCEC Contribution #14863, 2025 SCEC Annual Meeting Poster #TBD

Ambient-noise Horizontal-to-Vertical Spectral Ratio (HVSR) provides a cost-efficient estimate of a site’s fundamental frequency (f0​) using a single three-component sensor. Site specific geology is expected to significantly influence the HVSR peaks, trend of HVSR curve and f0. We deployed broadband seismometers simultaneously to synchronously record ~2 hours of ambient ground vibration data at representative different geologic settings (basin interior, basin edge, hill/mountain rock, and deep basin) in Los Angeles. Data acquisition at all four sites is done synchronously to reduce temporal variability in the noise field and enable direct, geology-driven influence of ambient vibration for comparisons of f0​. The goal is to isolate and understand geologic controls on the f0 derived from ambient-noise HVSR. Waveforms are preprocessed (de-trend, instrument correction, cosine taper, and band-pass filtered), windowed, and problematic windows are rejected prior to HVSR computation. Preliminary investigations show that although there is some difference in the estimated f0 from HVSR peak between the four different sites, the difference is not significantly distinct. We are working to identify site-specific controls (e.g., impedance contrast, sediment thickness, topography, and non-stationary ambient noise) that could explain the muted differences in f0.

Key Words
HVSR, fundemental frequency, Los Angeles Basin

Citation
Mansfield, R., K C, S., & Nweke, C. C. (2025, 09). Characterizing Fundamental Frequencies Across Geologies Using Ambient Noise HVSR. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Ground Motions (GM)