H/V Ratios in Northern California and the Livermore Basin

Brierton J. Sharp, Fan-Chi Lin, Taka'aki Taira, & Arthur J. Rodgers

Submitted August 30, 2026, SCEC Contribution #15225, 2026 SCEC Annual Meeting Poster #TBD

Despite the numerous active faults surrounding the Livermore Basin in northern California, its shallow velocity structure remains poorly constrained. To improve subsurface characterization and support seismic-hazard assessment, we deployed 197 seismometers across the basin from October 2025 through January 2026. We computed ambient-noise cross-correlation functions (CCFs) for all local station pairs and between the nodal array and 224 surrounding permanent stations. From these CCFs, we calculated Rayleigh-wave horizontal-to-vertical (H/V) ratios at periods ranging from 4 to 10 s. The observed H/V ratios within the Livermore Basin are substantially higher than those measured at surrounding permanent stations. They also exceed the ratios predicted within the basin by the San Francisco Community Velocity Model (SFCVM). This discrepancy suggests that the SFCVM underestimates the velocity gradient within the basin’s sedimentary layers. In future work, we will jointly invert the H/V ratios, phase velocities, and receiver functions using a Monte Carlo approach to construct a high-resolution, three-dimensional velocity model of the Livermore Basin.

Key Words
H/V Ratios, CVM, Tomography

Citation
Sharp, B. J., Lin, F., Taira, T., & Rodgers, A. J. (2026, 08). H/V Ratios in Northern California and the Livermore Basin. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology