Full microtremor H/V(z, f) inversion for shallow subsurface characterization

Lontsi, Agostiny Marrios; Sánchez‐Sesma, Francisco J.; Molina‐Villegas, Juan Camilo; Ohrnberger, Matthias; Krüger, Frank

doi:10.1093/gji/ggv132

Cited by 62 publications

(46 citation statements)

References 46 publications

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“…The meaning of the formula has theoretical support from deterministic exact solutions (Sánchez-Sesma, Weaver, et al, 2011). The proposed formula is also valid for observation at depth, as shown in a recent work by Lontsi et al (2015) in which the MHVRs observed by borehole receivers at different depths were used to invert S-and P-wave velocity structures. Another recent work on diffuse fields in layered media (García-Jerez et al, 2013) showed that their theoretical predictions for low-and high-frequency asymptotes from the separate calculation of various states (including P and S body waves and Love and Rayleigh waves) suggest that equipartition may arise in microtremors.…”

Section: Introductionmentioning

confidence: 67%

Applicability of Theoretical Horizontal-to-Vertical Ratio of Microtremors Based on the Diffuse Field Concept to Previously Observed Data

Kawase¹,

Matsushima²,

Satoh³

et al. 2015

Bulletin of the Seismological Society of America

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Horizontal-to-vertical spectral ratios of microtremors (MHVRs) have been interpreted as representing either the Rayleigh-wave ellipticity or the amplitude ratio of the sum of Rayleigh and Love waves in a horizontally layered structure. However, based on the recently established diffuse field concept, the theoretical form of MHVR has been proposed to be the square root of the ratio between the imaginary part of the horizontal Green's function on the surface and that of the vertical one. The theory assumes that the energy of a wavefield inside the earth will be equipartitioned among the various states in 3D space. In the case of microtremors, this may occur for randomly applied point-force loadings on the surface after sufficient lapse time to allow multiple scattering. Recent works on diffuse fields suggest that equipartition may arise in several ways, but understanding the emergence of equipartition in realistic settings requires further scrutiny. In the meantime, the resulting formula is quite simple, and its meaning has theoretical support from deterministic exact solutions. As references, we use observed microtremor data from several sites that were reported previously and validate the diffuse field method (DFM) as an alternative method to explain observed MHVR. We use only sites with reliable velocity structures to compare different methods quantitatively. As a result, we found that the DFM solutions with the corresponding 1D layered structures well explain the observed MHVRs for most of the sites. Thus, we believe that MHVR can be used to invert a 1D velocity structure by using DFM as a theoretical tool.

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Section: Introductionmentioning

confidence: 67%

Applicability of Theoretical Horizontal-to-Vertical Ratio of Microtremors Based on the Diffuse Field Concept to Previously Observed Data

Kawase¹,

Matsushima²,

Satoh³

et al. 2015

Bulletin of the Seismological Society of America

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“…The DFC theory for MHVR can be used for the velocity structure inversion. The validation studies of this DFC interpretation of MHVR can be found in Salinas et al (2014), Kawase et al (2015), and Lontsi et al (2015). Recently García-Jerez et al (2016) show a new calculation scheme using residue integrals, which is much more efficient in computing Green's functions and so they used it for velocity inversion.…”

Section: Introductionmentioning

confidence: 99%

Difference of horizontal-to-vertical spectral ratios of observed earthquakes and microtremors and its application to S-wave velocity inversion based on the diffuse field concept

Kawase

Mori

Nagashima

2018

Earth Planets Space

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We have been discussing the validity of using the horizontal-to-vertical spectral ratios (HVRs) as a substitute for S-wave amplifications after Nakamura first proposed the idea in 1989. So far a formula for HVRs had not been derived that fully utilized their physical characteristics until a recent proposal based on the diffuse field concept. There is another source of confusion that comes from the mixed use of HVRs from earthquake and microtremors, although their wave fields are hardly the same. In this study, we compared HVRs from observed microtremors (MHVR) and those from observed earthquake motions (EHVR) at one hundred K-NET and KiK-net stations. We found that MHVR and EHVR share similarities, especially until their first peak frequency, but have significant differences in the higher frequency range. This is because microtremors mainly consist of surface waves so that peaks associated with higher modes would not be prominent, while seismic motions mainly consist of upwardly propagating plain body waves so that higher mode resonances can be seen in high frequency. We defined here the spectral amplitude ratio between them as EMR and calculated their average. We categorize all the sites into five bins by their fundamental peak frequencies in MHVR. Once we obtained EMRs for five categories, we back-calculated EHVRs from MHVRs, which we call pseudo-EHVRs (pEHVR). We found that pEHVR is much closer to EHVR than MHVR. Then we use our inversion code to invert the one-dimensional S-wave velocity structures from EHVRs based on the diffuse field concept. We also applied the same code to pEHVRs and MHVRs for comparison. We found that pEHVRs yield velocity structures much closer to those by EHVRs than those by MHVRs. This is natural since what we have done up to here is circular except for the average operation in EMRs. Finally, we showed independent examples of data not used in the EMR calculation, where better ground structures were successfully identified from pEHVRs again. Thus we proposed here a simple empirical method to estimate S-wave velocity structures using single-station microtremor records, which is the most cost-effective method to characterize the site effects.Keywords: Site effect, Subsurface structure, Seismological bedrock, Horizontal-to-vertical ratio, Hybrid heuristic search, S-wave, P-wave © The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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“…matrix Figure 2. Normalized energy density profiles (Im(G 11 ), Im(G 22 ), Im(G 33 ), and the total directional energy density) for the three orthogonal directions estimated using (1) the algorithm based on the propagator matrix formulation (thin continuous line) and (2) the algorithm based on the global matrix formulation for a layered medium (dashed thick line; Lontsi et al 2015). The depth is normalized with the Rayleigh wavelength.…”

Section: Considerations For Numerical Implementationmentioning

confidence: 99%

A generalized theory for full microtremor horizontal-to-vertical [H/V(z, f)] spectral ratio interpretation in offshore and onshore environments

Lontsi

García‐Jerez

Molina‐Villegas

et al. 2019

Geophysical Journal International

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Advances in the field of seismic interferometry have provided a basic theoretical interpretation to the full spectrum of the microtremor horizontal-to-vertical spectral ratio [H/V (f )]. The interpretation has been applied to ambient seismic noise data recorded both at the surface and at depth. The new algorithm, based on the diffuse wavefield assumption, has been used in inversion schemes to estimate seismic wave velocity profiles that are useful input information for engineering and exploration seismology both for earthquake hazard estimation and to characterize surficial sediments. However, until arXiv:1907.04606v1 [physics.geo-ph]

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Full microtremor H/V(z, f) inversion for shallow subsurface characterization

Cited by 62 publications

References 46 publications

Applicability of Theoretical Horizontal-to-Vertical Ratio of Microtremors Based on the Diffuse Field Concept to Previously Observed Data

Applicability of Theoretical Horizontal-to-Vertical Ratio of Microtremors Based on the Diffuse Field Concept to Previously Observed Data

Difference of horizontal-to-vertical spectral ratios of observed earthquakes and microtremors and its application to S-wave velocity inversion based on the diffuse field concept

A generalized theory for full microtremor horizontal-to-vertical [H/V(z, f)] spectral ratio interpretation in offshore and onshore environments

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