Determination of shallow crustal structure in Northern California and community model validation using ambient-noise-derived Rayleigh wave ellipticity and receiver functions: Preliminary results

Gabriela A. Zaldivar Andrade, HyeJeong Kim, Fan-Chi Lin, & Taka'aki Taira

Published September 8, 2024, SCEC Contribution #13896, 2024 SCEC Annual Meeting Poster #044 (PDF)

Northern California has several active faults prone to large-magnitude earthquakes, such as the Hayward Fault in the San Francisco Bay Area. A three-dimensional (3D) seismic velocity model is a key component in evaluating ground motion predictions for large earthquakes. The regional Northern California USGS seismic velocity model (USGS_SVM) has been continuously refined to reduce misfit between the predicted and observed ground motion through 3D ground-motion simulations body wave travel times, and surface wave dispersion measurements (e.g., Hirakawa and Aagaard, 2022; Hao et al., 2024). Recent studies have suggested that Rayleigh wave ellipticity (H/V) from ambient seismic noise cross-correlations and the first peak of a receiver function (RF) are particularly sensitive to shallow crustal structures. Rayleigh wave phase velocity, H/V, and RFs have successfully imaged the sedimentary basin of Southern California (Berg et al., 2018). In this study, we compute nine-component ambient noise cross-correlation functions from 90 broadband stations installed in North California with data collected between November 2020 and January 2021. We measure the Rayleigh wave ellipticity H/V in the period from 6 to 26 s and produce period-dependent H/V maps. These maps reveal higher H/V ratios in the Central Valley and Coastal Ranges, with lower ratios in the Sierra Nevada and northern areas such as Clear Lake, throughout the period range analyzed. RFs are calculated from teleseismic earthquake data using the broadband and short-period stations available between 2014–2024; we measured the first peak delay time of RF at each station. The RF results show large delay times in the Central Valley. In this presentation, we will show the preliminary results of the measured H/V and RF peak delay times and will compare our measurements with predictions from the USGS_SVM. These results, combined with other available measurements, will help to construct an improved 3D crustal model and serve as a reference model for future SVM updates.

Key Words
Rayleigh wave ellipticity, Ambient Noise, Receiver Functions, Surface Waves, North California, Seismic Velocity Model

Citation
Zaldivar Andrade, G. A., Kim, H., Lin, F., & Taira, T. (2024, 09). Determination of shallow crustal structure in Northern California and community model validation using ambient-noise-derived Rayleigh wave ellipticity and receiver functions: Preliminary results. Poster Presentation at 2024 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology