Full Waveform Inversion Tomography of the San Francisco Bay Area

Arthur J. Rodgers, Claire Doody, Jiun-Ting Lin, & Qingkai Kong

Submitted August 30, 2026, SCEC Contribution #15141, 2026 SCEC Annual Meeting Poster #TBD

We present a new three-dimensional seismic-wave-speed model for the San Francisco Bay Area (SFBA) inferred from full waveform inversion of local earthquake data. The 160 km by 160 km model domain covers San Francisco, San Jose, Oakland, the East Bay, Sacramento-San Joaquin Delta, Marin and adjacent offshore regions. We selected broadband waveforms from moderate moment magnitude (MW 3.5-5.5) earthquakes with Berkeley Seismology Laboratory moment tensors. Starting from the plane-layered GIL7 model (Dreger and Romanowicz, 1994) modified with a smooth Moho, we inverted time-frequency phase misfits in five stages, progressively reducing the minimum period from 15 to 5 seconds. The resulting model (SFBA3D) reveals strong lateral heterogeneity and improves waveform fits relative to the starting model and alternative models of the region, including the USGS geology-based model (Hirakawa and Aagaaard, 2021), the travel time and ambient noise dispersion inversion model of Guo et al. (2025), and the MUSCAL multiscale merged model of Yeh et al. (2026). The SFBA3D model shows strong wavespeed contrasts across the Calaveras and Hayward Faults consistent with geological mapping and previous tomography studies. It also infers low shear wavespeeds in the sedimentary basins of the Delta, Livermore, Evergreen and San Leandro Basins, the San Pablo Bay and the Gulf of Farallones. These results show that waveform inversion tomography starting with a simple laterally homogenous model and with good data coverage can reliably image strong 3D wavespeed heterogeneity associated with known geologic features. Importantly, the new model improves waveform fits over the 5-30 s band and could be used for ground motion simulations, event characterization (e.g. moment tensor of finite fault inversions) or for further higher-resolution structure inversions.

Key Words
tomography, ground motion simulation

Citation
Rodgers, A. J., Doody, C., Lin, J., & Kong, Q. (2026, 08). Full Waveform Inversion Tomography of the San Francisco Bay Area. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Community Earth Models (CEM)