Validation of a New Velocity Structure Inversion Method Based on Horizontal-to-Vertical (H/V) Spectral Ratios of Earthquake Motions in the Tohoku Area, Japan

Ducellier, Ariane; Kawase, Hiroshi; Matsushima, Shinichi

doi:10.1785/0120120214

Cited by 29 publications

(15 citation statements)

References 37 publications

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“…The square root of the bedrock's P-and S-wave velocity ratio is used as a correction coefficient for the incident wave amplitude. The validity of the method used to derive underground S-wave structures from EHVRs has been reported by Ducellier et al (2013) and Nagashima et al (2014). On the other hand, Salinas et al (2014) compared observed EHVR and MHVR at one site inside the Mexico City basin and found that the observed EHVR is similar to the theoretical MHVR, especially in the high-frequency range.…”

Section: Introductionmentioning

confidence: 70%

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: 70%

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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“…Then, Kawase et al (2011) extended the idea of DFC to the stack of horizontal-to-vertical ratios of earthquakes (EHVR) and provided a simple theoretical formula assuming equipartition of energy in the incident waves at the bedrock (i.e., equipartition inside the half-space). It turned out that this is a powerful tool to determine the S-wave velocity structure below the observed site of earthquakes down to the seismological bedrock, as evidenced by Ducellier et al (2013), Nagashima et al (2014Nagashima et al ( , 2017 and Fukihara et al (2015).…”

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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“…On the contrary, the resolution of 1-D seismic profiles depends on the distance between acquisitions points with borehole measurements that can be averaged to get smooth variations (Moss 2008). Arai & Tokimatsu (2005) and Ducellier et al (2011) among others performed a sensitivity analysis to determine which soil parameters controlled, in the inversion process, the H/V (horizontal to vertical) curves obtained from seismic ambient noise measurements, defined on a specific frequency range. Moreover, the resolution provided by each method must be kept in mind while building a numerical model based on real data.…”

mentioning

confidence: 99%

Influence of a sedimentary basin infilling description on the 2-D P–SV wave propagation using linear and non-linear constitutive models

Gelis¹,

Bonilla

2014

Geophysical Journal International

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S U M M A R YNumerical modelling is a useful tool to understand the role of different parameters (site geometry, impedance contrast, material properties, constitutive model, input motion) governing site effects. We focus here on the 2-D P-SV seismic wave propagation in a simple-shaped asymmetric model. We consider two ways of describing the sedimentary infilling properties: the basin is either composed of distinct homogeneous geological layers or is described through properties progressively changing as a function of depth (smooth model). In order to study the wave propagation in the two basins with similar soil properties, P and S velocities of the layered basin are deduced from the smooth basin ones, making both models compatible in a kinematic point of view. P and S velocities globally increase with depth. Following EPRI, non-linear properties are considered as constant in layers for the two basins. We assess the influence of the model choice on the wave propagation while taking into account linear and non-linear constitutive models. We test the influence of the input motion by propagating two different input motions, the first being a simple impulsive one and the second a real complex accelerogram. We find that transfer functions computed in each basin are quite similar irrespective of the soil constitutive behaviour and the input motion. Moreover, we show that the maximum shear strain spatial distribution depends on the input motion frequency content and maximum values depend on the input motion strength and complexity. Maximum shear strains are generally higher for superficial layers than for deeper ones. We show that the highest shear strain values are located above discontinuities, where velocities are lower and the soil is more non-linear than in the underlying layer, regardless of the input motion. Indeed, in a layered basin, the shear strain is higher above interfaces for all the soil constitutive models that were used. In the smooth visco-elastoplastic model, a kind of layering appears, absent in a viscoelastic model, due to the different non-linear properties in each layer. Moreover, no matter what the model structure and the input motion used, maximum shear strain levels are higher in the visco-elastoplastic soil than in the viscoelastic one. Such a numerical study helps to understand the non-linearity location and therefore the consequences of a model choice when performing a site-specific study.

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Validation of a New Velocity Structure Inversion Method Based on Horizontal-to-Vertical (H/V) Spectral Ratios of Earthquake Motions in the Tohoku Area, Japan

Cited by 29 publications

References 37 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

Influence of a sedimentary basin infilling description on the 2-D P–SV wave propagation using linear and non-linear constitutive models

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