Depth of sudden velocity increases from multi-mode Rayleigh waves derived with three-component ambient noise beamforming

• DOI: 10.5194/egusphere-egu23-12396
• Publication Date: 2023-02-26T02:28:33Z
• Authors: Claudia Finger; Katrin Löer
• Keywords: Rayleigh Wave; Phase velocity; Group velocity; Ellipse; Dispersion relation

Surface wave dispersion curves derived from ambient noise recordings are frequently used to invert for subsurface velocity information. Rayleigh ellipticities and phase velocities exploited, sometimes jointly inverted, the structure beneath seismic arrays. Wavelengths of surface waves become large at low frequencies are, thus, sensitive great depths, but provide only very smooth profiles. However, sudden increases in particular interest delineate extent reservoirs, i.e., by sub-horizontal faults or detachments, estimate depth sedimentary basins.Here, we report a new approach vertical profiles using velocities. Using Kepler’s law motion on elliptical orbits, can theoretically frequency-dependent half-height half-width energy ellipse described waves.In presence increases, fundamental first higher mode have similar so-called osculation frequency. This often leads misidentification that biases inversion results. We show this frequency is close where ellipticity one, circular, has its maximum. At frequency, our relation requires ellipse, which good approximation increase.To derive synthetic three-component waveforms real-world datasets three sites (Weisweiler Germany, FORGE Utah, USA Groningen, Netherlands), use beamforming, provides polarization parameters recorded short time windows thus distinguish types modes. From identified waves, pick directly beamformer plots relation. No scheme needed approach.This more accurate estimates jumps than other methods. The sensitivity limited inter-station distances array configuration useable range. depths be constrain schemes models map structural changes subsurface.