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

Lontsi, Agostiny Marrios; García‐Jerez, Antonio; Molina‐Villegas, Juan Camilo; Sánchez‐Sesma, Francisco J.; Molkenthin, Christian; Ohrnberger, Matthias; Wang, Rongjiang; Fäh, Donat

doi:10.1093/gji/ggz223

Cited by 15 publications

(4 citation statements)

References 46 publications

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“…3, the maximum of the peak amplitudes varies through time by a factor from 1.5 (SS13 and SS22) to 2 (SS08 and SS19). In the same way, the peak frequencies also vary at maximum by 10 per cent, which is commonly assumed as a marginal variation (SESAME Project 2004;Lontsi et al 2019).…”

Section: R E S U Lt Smentioning

confidence: 99%

“…Both peak and resonance frequency, when they exist, are related to the impedance contrast between the sediment layer and the bedrock. In some cases, HVSR curves have two or more peaks which can correspond, for frequencies higher than f 0 , to higher harmonic modes of the first peak, linked to multiple reflection of S waves in the sediment layer (Bonnefoy-Claudet et al 2006), or, mainly for the second peak, to the existence of another strong impedance contrast in the sedimentary cover (Cornou et al 2003;Mucciarelli 2011;Harutoonian et al 2013;Moisidi et al 2015;Lontsi et al 2019). Due to local geometry and 3-D structural complexities, the HVSR results are often combined with other experimental observations such as borehole, geological and geophysical data (Moisidi et al 2015;Fehr et al 2019).…”

Section: Introductionmentioning

confidence: 99%

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Seasonal variations in amplitudes and resonance frequencies of the HVSR amplification peaks linked to groundwater

Rigo

Sokos

Lefils

et al. 2021

Geophysical Journal International

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Following the installation of a temporary seismological network in western Greece north of the Gulf of Patras, we determined the quality of the sites of each of the 10 stations in the network. For this, we used the horizontal-to-vertical spectral ratio (HVSR) method and calculated an average curve over randomly selected days between 0 Hz and 10 Hz. The daily HVSR curve is determined by the HVSR 12-hour calculation (one hour every two) without distinction between seismic ambient noise and earthquake signal. The HVSR curves obtained can be classified in three categories: flat curves without amplification, curves with a amplification peaks covering a large frequency range, and curves with one or more narrow peaks. In this third category C3, one station has one peak, two have two, and one has three. On the contrary of what it is commonly assumed, the amplitudes and the resonance frequencies of these narrow peaks are not stable over time in C3. We determined the maximum of the amplitude of each peak with the corresponding central frequency for each day during 2.5 years. Except for the station with three peaks, which finally appears stable within the uncertainties, the principal peak exhibits a seasonal variation, with a maximum in winter and a minimum in summer, the observations being more dispersed during winter. The second peak, when it exists, varies in the same way except at one station where it varies oppositely. These variations are clearly correlated with the loading and unloading cycle of the underlying aquifers as shown by the comparison with water level and yield measurements from wells located close to the stations. Moreover, they are also correlated with the vertical surface displacements observed at continuously recording GPS stations. The dispersion of the observed maximum amplitude in winter is probably related to the rainfall and the soil moisture modifying the S-wave velocity as revealed by other studies. From this study, we would like to emphasize that the use the HVSR method to constrain the S-wave velocity and the thickness of the sediment layer over the bedrock in the basin, has to be done with caution. Upon further confirmation of its robustness, the HVSR methodology presented here could be a good and easy-to-use tool for a qualitative survey of the aquifer backdrop and its seasonal behaviour, and of the soil moisture conditions.

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Section: R E S U Lt Smentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Seasonal variations in amplitudes and resonance frequencies of the HVSR amplification peaks linked to groundwater

Rigo

Sokos

Lefils

et al. 2021

Geophysical Journal International

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“…The MHVSR is modeled in terms of Green’s functions: where ImG ii is the imaginary part of the Green’s function for the ith component for a unit harmonic excitation in the ith direction when both source and receiver coincide. For a horizontally layered medium, this approach is straightforward for surface recordings (Sánchez-Sesma et al 2011 ; Kawase et al 2015 ) and at depth (Lontsi et al 2015 ) and even under a water layer in offshore settings (Lontsi et al 2019 ). Considering the microtremor wavefield as not systematically diffuse and equipartitioned, Tchawe et al ( 2020 ) proposed to compute MHVSR on the coda part of the microtremor correlations.…”

Section: Theoretical Background: State Of Knowledge and Ongoing Debatesmentioning

confidence: 99%

A review of the microtremor horizontal-to-vertical spectral ratio (MHVSR) method

et al. 2022

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The single-station microtremor horizontal-to-vertical spectral ratio (MHVSR) method was initially proposed to retrieve the site amplification function and its resonance frequencies produced by unconsolidated sediments overlying high-velocity bedrock. Presently, MHVSR measurements are predominantly conducted to obtain an estimate of the fundamental site frequency at sites where a strong subsurface impedance contrast exists. Of the earthquake site characterization methods presented in this special issue, the MHVSR method is the furthest behind in terms of consensus towards standardized guidelines and commercial use. The greatest challenges to an international standardization of MHVSR acquisition and analysis are (1) the what — the underlying composition of the microtremor wavefield is site-dependent, and thus, the appropriate theoretical (forward) model for inversion is still debated; and (2) the how — many factors and options are involved in the data acquisition, processing, and interpretation stages. This paper reviews briefly a historical development of the MHVSR technique and the physical basis of an MHVSR (the what). We then summarize recommendations for MHVSR acquisition and analysis (the how). Specific sections address MHVSR interpretation and uncertainty assessment.

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“…While it is predominantly a tool for soft sediment thickness estimations and seismic hazard analysis [ 5 , 6 ], it draws increasing attention for permafrost depth estimation [ 7 , 8 , 9 ] and various subsurface characterisation purposes [ 10 , 11 , 12 , 13 , 14 , 15 ]. Among its advantages are practicality and cost efficiency [ 16 ], partly because, with very little additional effort, it is a by-product of most seismic survey campaigns that employ three component (3C) instruments. Therefore, the question arises as to whether or not principal seismic techniques, for which extensive large-N surveys are designed, can benefit from processing and analysing this essentially free data derivative even though the surveys’ targets may be beyond typical HVSR capabilities.…”

Section: Introductionmentioning

confidence: 99%

On the Utility of Horizontal-to-Vertical Spectral Ratios of Ambient Noise in Joint Inversion with Rayleigh Wave Dispersion Curves for the Large-N Maupasacq Experiment

Neukirch

García‐Jerez

Villaseñor

et al. 2021

Sensors

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Horizontal-to-Vertical Spectral Ratios (HVSR) and Rayleigh group velocity dispersion curves (DC) can be used to estimate the shallow S-wave velocity (VS) structure. Knowing the VS structure is important for geophysical data interpretation either in order to better constrain data inversions for P-wave velocity (VP) structures such as travel time tomography or full waveform inversions or to directly study the VS structure for geo-engineering purposes (e.g., ground motion prediction). The joint inversion of HVSR and dispersion data for 1D VS structure allows characterising the uppermost crust and near surface, where the HVSR data (0.03 to 10s) are most sensitive while the dispersion data (1 to 30s) constrain the deeper model which would, otherwise, add complexity to the HVSR data inversion and adversely affect its convergence. During a large-scale experiment, 197 three-component short-period stations, 41 broad band instruments and 190 geophones were continuously operated for 6 months (April to October 2017) covering an area of approximately 1500km2 with a site spacing of approximately 1 to 3km. Joint inversion of HVSR and DC allowed estimating VS and, to some extent density, down to depths of around 1000m. Broadband and short period instruments performed statistically better than geophone nodes due to the latter’s gap in sensitivity between HVSR and DC. It may be possible to use HVSR data in a joint inversion with DC, increasing resolution for the shallower layers and/or alleviating the absence of short period DC data, which may be harder to obtain. By including HVSR to DC inversions, confidence improvements of two to three times for layers above 300m were achieved. Furthermore, HVSR/DC joint inversion may be useful to generate initial models for 3D tomographic inversions in large scale deployments. Lastly, the joint inversion of HVSR and DC data can be sensitive to density but this sensitivity is situational and depends strongly on the other inversion parameters, namely VS and VP. Density estimates from a HVSR/DC joint inversion should be treated with care, while some subsurface structures may be sensitive, others are clearly not. Inclusion of gravity inversion to HVSR/DC joint inversion may be possible and prove useful.

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

Cited by 15 publications

References 46 publications

Seasonal variations in amplitudes and resonance frequencies of the HVSR amplification peaks linked to groundwater

Seasonal variations in amplitudes and resonance frequencies of the HVSR amplification peaks linked to groundwater

A review of the microtremor horizontal-to-vertical spectral ratio (MHVSR) method

On the Utility of Horizontal-to-Vertical Spectral Ratios of Ambient Noise in Joint Inversion with Rayleigh Wave Dispersion Curves for the Large-N Maupasacq Experiment

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