SCEC Award Number 23129 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title High-resolution seismic imaging of Los Angeles Basin using data from a dense geophone seismic array
Investigator(s)
Name Organization
Fan-Chi Lin University of Utah Robert Clayton California Institute of Technology
Other Participants Konstantinos Gkogkas
SCEC Priorities 4b, 4c, 1c SCEC Groups Seismology, CXM, GM
Report Due Date 03/15/2024 Date Report Submitted 05/05/2024
Project Abstract
 We deployed a temporary nodal array in the Los Angeles basin, comprising of ~270 nodal geophone seismometers, structured by two dense lines (inter-station spacing of ~0.6 km) and a 2D distributed/shotgun array (spacing of ~2 km). We compute multi-component ambient-noise cross-correlations between all stations available in the area, including both regional broadband and nodal stations. We observe clear fundamental mode Rayleigh waves in the period band of 5-9s and measure the Rayleigh wave ellipticity, or H/V (Horizontal-to-Vertical) amplitude ratios. The measured Rayleigh wave ellipticity clearly depicts the basin's lateral boundaries. We compare our findings with predictions based on the SCEC Community Velocity Model (CVM) and discuss how the model can be further improved. At each station, we also examine the azimuthal dependency of the ellipticity measurements. Further studies will be needed to isolate structural anisotropy from azimuthal variation caused by wavefield complexity.
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 can be reliably measured across a temporary nodal geophone array in the Los Angeles Basin. Such measurements are particularly sensitivity to shallow basin structure and could be used to improve the CVM.
Broader Impacts A PhD student, Kostas Gkogkas, was supported by the SCEC project. The student has successfully defended his thesis and will move on to take an academic position in Europe. The nodal seismic data collected across the Los Angeles Basin has been achieved in IRIS DMC.
Exemplary Figure Figure 3.
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