SCEC Award Number 24098 View PDF
Proposal Category Collaborative Research Project (Multiple Investigators / Institutions)
Proposal Title Determination of Shallow Crustal Structure in Northern California and Community Model Validation Using Ambient-noise-derived Rayleigh Wave Ellipticity and Receiver Functions
Investigator(s)
Name Organization
Fan-Chi Lin University of Utah Taka'aki Taira University of California, Berkeley
SCEC Milestones A1-1, A2-1, A3-6, D3-2 SCEC Groups Seismology, CEM, GM
Report Due Date 03/15/2025 Date Report Submitted 03/31/2025
Project Abstract
 Northern California contains numerous active faults, including the Hayward Fault near the San Francisco Bay Area, which is capable of generating large-magnitude (M > 6) earthquakes with potentially severe impacts. Accurate three-dimensional (3D) seismic velocity models, particularly those that capture detailed uppermost crustal structure, are crucial for predicting ground motions during such events. In this project, we analyze multi-component ambient noise and teleseismic receiver function (RF) data from both permanent and temporary seismic stations across northern California. We derive two independent measurements—Rayleigh wave H/V ratios and RF initial phase delay times—both of which provide sensitivity to uppermost crustal structure. These observations are then compared with predictions from the USGS_SVM CVM model. Our results show that while the CVM model performs well at a regional scale, its representation of sedimentary structure can be further refined by incorporating H/V ratio and RF measurements. Beyond CVM validation, we demonstrate that the thick sedimentary deposits within the Central Valley excite higher-mode surface waves, complicating the measurement of Rayleigh wave H/V ratios.
SCEC Community Models Used Community Velocity Model (CVM)
Usage Description We used the CMV to forward calculate Rayleigh wave H/V ratios and receiver function initial phase delay time. The comparison between the observations and predictions is then used to validate the CVM.
Intellectual Merit An accurate CVM model is critical to accurately prediction earthquake ground motion. In this study, we demonstrate that robust Rayleigh wave H/V ratios and receiver function initial phase delay time can be reliably measured across both the permanent and temporary seismic stations across the Northern California. Such measurements are particularly sensitivity to shallow basin structure and could be used to validate and improve the CVM. We also demonstrate how Rayleigh wave H/V ratio measurements can be complicated by the presence of higher mode in thick sedimentary environment.
Broader Impacts The project helped to support one female postdoc, HyeJeong Kim, and one female El Salvador MS student, Gabriela Zaldivar Andrade. The MS student is on track to graduate in summer 2025 and will move on to pursue a PhD degree in another institute. Metadata problems including station orientation issues have been reported by to the seismic network coordinators.
Project Participants PI at the University of Utah: Fan-Chi Lin
PI at the University of California Berkeley: Taka'aki Taira
Postdoc at the University of Utah: HyeJeong Kim
Graduate student at the University of Utah: Gabriela Zaldivar Andrade
Exemplary Figure Figure 5. Receiver function initial phase delay time map showing individual station results overlaid on predicted delay time values predicted by the USGS_SVM model in the background (left) The entire area. (upper right) Zoom into the Bay area. (lower left) Zoom into southern Central Valley. Clear discrepancies between the observed and predicted receiver function delay time can be observed within the Sacramento-San Joaquin Delta east of the Bay Area and Central Valley.
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