<p>Surface-wave analysis can be performed according to a multitude of approaches. In fact, both the determination of the dispersive properties and data inversion can be accomplished according to several possible techniques, which should be chosen on a case-by-case basis, depending on the goals and site characteristics. The <i>Miniature Array Analysis of Microtremors</i> (MAAM) is an interesting methodology aimed at extracting the dispersive properties of the vertical (Z) component of Rayleigh waves from passive data recorded according to a circular-symmetry array. Compared to other techniques, MAAM can investigate larger wavelengths and provide phase velocities in a wider frequency range (a triangular array with a radius of a couple of meters can provide the dispersion curve in the 2–20&#xa0;Hz frequency range, approximatively). Despite its remarkable potential, MAAM can be affected by industrial noise that alters the natural microtremor field. The comparative analysis of the Z-component dispersion retrieved via <i>Extended Spatial AutoCorrelation</i> (ESAC) and MAAM is initially conducted to validate the adopted procedures and verify the paradigms to adopt to identify the frequency range properly investigated. Following this, analysing a second time-lapse dataset, the effects of industrial components on both the dispersion curve obtained via MAAM and the Horizontal-to-Vertical Spectral Ratio (HVSR) are investigated. The experimental evidences show that non-monochromatic industrial components can have a malicious effect on both MAAM and HVSR. In this context, analysing the coherence functions of the multi-component data recorded by a 3-component geophone, together with the spectral ratio and noise-to-signal ratio obtained during MAAM processing, is crucial for assessing the possible presence of industrial components that may affect the observables ultimately used in the joint inversion.</p>

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Possible Effects of Industrial Components on the Miniature Array Analysis of Microtremors and Horizontal-to-Vertical Spectral Ratio (with Some Notes on Their Joint Inversion)

  • Giancarlo Dal Moro

摘要

Surface-wave analysis can be performed according to a multitude of approaches. In fact, both the determination of the dispersive properties and data inversion can be accomplished according to several possible techniques, which should be chosen on a case-by-case basis, depending on the goals and site characteristics. The Miniature Array Analysis of Microtremors (MAAM) is an interesting methodology aimed at extracting the dispersive properties of the vertical (Z) component of Rayleigh waves from passive data recorded according to a circular-symmetry array. Compared to other techniques, MAAM can investigate larger wavelengths and provide phase velocities in a wider frequency range (a triangular array with a radius of a couple of meters can provide the dispersion curve in the 2–20 Hz frequency range, approximatively). Despite its remarkable potential, MAAM can be affected by industrial noise that alters the natural microtremor field. The comparative analysis of the Z-component dispersion retrieved via Extended Spatial AutoCorrelation (ESAC) and MAAM is initially conducted to validate the adopted procedures and verify the paradigms to adopt to identify the frequency range properly investigated. Following this, analysing a second time-lapse dataset, the effects of industrial components on both the dispersion curve obtained via MAAM and the Horizontal-to-Vertical Spectral Ratio (HVSR) are investigated. The experimental evidences show that non-monochromatic industrial components can have a malicious effect on both MAAM and HVSR. In this context, analysing the coherence functions of the multi-component data recorded by a 3-component geophone, together with the spectral ratio and noise-to-signal ratio obtained during MAAM processing, is crucial for assessing the possible presence of industrial components that may affect the observables ultimately used in the joint inversion.