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- Title
Depth of Sudden Velocity Changes Derived From Multi‐Mode Rayleigh Waves.
- Authors
Finger, C.; Löer, K.
- Abstract
To integrate structural subsurface models and smooth seismic velocity models, they need to share common features and resolutions. Here, we propose a new approach, Depth Assessment from Rayleigh Wave Ellipticities (DARE), for estimating the depth of sudden velocity changes from ambient‐noise multi‐mode Rayleigh waves applicable to a wide range of frequencies. At frequencies where multi‐mode Rayleigh waves have an extremum in ellipticity, the phase velocity can be used to estimate the depth of sudden velocity changes. We test our approach theoretically, numerically, and on real data from two geothermal sites by extracting Rayleigh wave ellipticities and phase velocities from three‐component beamforming of ambient noise using the python code package B3AMpy. For a small‐scale array, our approach validates the depth of quaternary sediments predicted by geological models. For deeper velocity changes, high uncertainties remain but the general trend of inclining boundaries can be recovered well. We demonstrate that, if impedance contrasts are larger than three, our approach is valid for multiple layers, laterally heterogeneous models, and a wide range of Poisson ratios. Plain Language Summary: To effectively combine structural models and seismic velocity models, we've developed a new method. It estimates the depth of sudden changes in seismic velocity using Rayleigh waves from ambient noise. By identifying minima and maxima in Rayleigh wave ellipticity, we determine the depth of sudden velocity changes from the observed phase velocity at that point. We tested the method and found it works well for various scenarios, including multiple layers, heterogeneous models, and different material properties. This new Rayleigh wave method could be useful in seismic hazard studies to determine the depth of sedimentary basins. Key Points: We estimate the depth of sudden velocity increases from phase velocity and ellipticity of ambient‐noise multi‐mode Rayleigh wavesThree‐component ambient‐noise beamforming is used to estimate phase velocity and ellipticityFeasibility is demonstrated with noise recordings from multiple sites and validated with results from other studies
- Subjects
SURFACE waves (Seismic waves); POISSON'S ratio; RAYLEIGH waves; SEISMIC wave velocity; PHASE velocity; VELOCITY; SEDIMENTARY basins
- Publication
Journal of Geophysical Research. Solid Earth, 2024, Vol 129, Issue 3, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2023JB028322