3D Seismic Attenuation Model: Scattering and Absorption Imaging Beneath the Los Angeles Metropolitan Area
Description:
In high seismic hazard regions, modelling seismic attenuation and combining it with velocity models is a powerful tool for imaging crustal features, such as complex fault systems, sedimentary layers and fluids. A frequency-dependent attenuation model is also critical for improving wavefield predictions in ground motion studies.
In the northern Los Angeles area, sedimentary basins may act as a waveguide producing large amplifications from an earthquake rupture on the southern San Andreas Fault. While the Southern California Earthquake Center community models provide P and S wave velocities for this region, a 3D attenuation model has to be incorporated into Earth models for more accurate wavefield simulations. This work aims to develop the first high-resolution, physics-based attenuation model across the Chino and San Bernardino basins using local earthquakes recorded by eight nodal arrays (410 stations), deployed during the Basin Amplification Seismic Investigation (BASIN) experiment. We perform high-frequency attenuation analysis using the peak-delay and coda attenuation methods to measure the scattering and absorption contributions, respectively. We present seismic scattering and intrinsic attenuation tomography at 12, 18, and 24 Hz (down to 10 km depth with a horizontal and depth resolution of 3 km and 1 km, respectively). The results show that the main structural discontinuities, such as the Fontana fault in the Chino basin, control the scattering anomalies allowing for the discrimination between relatively compact and fractured media. High absorption anomalies across the basins mark sedimentary layers and suggest the presence of fluids, i.e., groundwater, in agreement with recent ambient noise tomography. We thus present imaging results of both elastic and anelastic properties that aim at constraining the effects of sediments, fluids, and fractures on seismic wave propagation beneath the Los Angeles metropolitan area.
Session: Crustal Imaging of High Seismic Hazard Regions
Type: Oral
Date: 4/20/2023
Presentation Time: 10:45 AM (local time)
Presenting Author: Chiara Nardoni
Student Presenter: No
Invited Presentation:
Authors
Chiara Nardoni Presenting Author Corresponding Author cnardoni@lsu.edu Louisiana State University |
Patricia Persaud ppersaud@lsu.edu University of Arizona |
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3D Seismic Attenuation Model: Scattering and Absorption Imaging Beneath the Los Angeles Metropolitan Area
Category
Crustal Imaging of High Seismic Hazard Regions