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Improving the Salt Lake Basin Velocity Model Using Multi-Year Nodal Geophone Arrays

Description: 

An accurate high-resolution velocity model is critical for evaluating the ground shaking hazard from moderate to large local earthquakes. The current community velocity model (CVM) for the Salt Lake Basin in Utah was constructed mostly based on legacy gravity measurements, supplemented by sparsely distributed well logs and legacy active-source seismic profiles. Since 2018, the seismic data coverage of the Basin has substantially improved with the addition of data from three nodal geophone experiments: a 2018 32-node linear array across the East Bench fault of the Salt Lake City segment of the Wasatch fault zone, a 2020 217-node Magna earthquake (M_w 5.7) aftershock array, and a 2023 38-node multi-month distributed array deployed to investigate hydro-geophysical signals. In this presentation, we will summarize our recent effort to improve the Salt Lake Basin CVM by adding new constraints derived from the nodal data. Specifically, we will show that the first positive peak of receiver functions in the Salt Lake Basin is sensitive to the P-to-S conversion at the base of the semi-consolidated sediment layer, which rapidly changes depth across the East Bench fault. Moreover, good correlations exist between the delay time of the first receiver function peak, Rayleigh wave ellipticity, and the local gravity anomaly, demonstrating the potential of jointly inverting the three datasets to refine the 3D basin model. We have determined a preliminary model by jointly inverting receiver function waveforms and Rayleigh wave ellipticities plus phase velocities. The results indicate a greater thickness of unconsolidated and semi-consolidated sediments, compared to the existing CVM, between the East Bench fault and the West Valley fault zone. This area underlies the most densely populated parts of Salt Lake City. Our new velocity model will contribute to improved earthquake hazard assessments by enabling more accurate numerical ground motion simulations for realistic earthquake scenarios.

Session: Earth’s Structure from the Crust to the Core - I

Type: Oral

Date: 5/1/2024

Presentation Time: 08:30 AM (local time)

Presenting Author: HyeJeong

Student Presenter: No

Invited Presentation: 

Authors