OpenHVSR: imaging the subsurface 2D/3D elastic properties through multiple HVSR modeling and inversion

Bignardi, Samuel; Mantovani, A.; Zeid, Nasser Abu

doi:10.1016/j.cageo.2016.05.009

Cited by 86 publications

(38 citation statements)

References 14 publications

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“…Moreover, in this paper, we have demonstrated that a detailed study of the full H/V shape can provide information about geological structure of the measurement site. In this regard, different methodologies have recently been developed in order to obtain the

V_{s}

profile from the inversion of the full H/V spectral ratio curve (Sánchez‐Sesma et al ; García‐Jerez et al ; Bignardi, Mantovani and Abu Zeid ). A comparison between the zonation according to the H/V shapes found in the urban area of Girona and the geological map shows a good agreement.…”

Section: Discussionmentioning

confidence: 99%

“…The expression S/R proposed by Ibs-von Seht and Wohlenberg (1999) shows the best fit for our results on array data, between 0.4 Hz and 7 Hz. Figure 13 presents the bedrock topography (i.e., sediment thickness) interpolated from 170 values of the soil fundamental frequency and the equation proposed by Ibs-von Seht and Parolai et al (2002) 108 −1.551 Benjumea et al (2011) 108 −0.82 Kühn et al (2011) 125 −1.07 in order to obtain the V s profile from the inversion of the full H/V spectral ratio curve (Sánchez-Sesma et al 2011;García-Jerez et al 2016;Bignardi, Mantovani and Abu Zeid 2016). A comparison between the zonation according to the H/V shapes found in the urban area of Girona and the geological map shows a good agreement.…”

Section: Discussionmentioning

confidence: 99%

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Geophysical measurements for site effects characterisation in the urban area of Girona, Spain

Macau

Benjumea

Gabàs

et al. 2018

Near Surface Geophysics

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Amplitude level, duration, and spectral content of earthquake ground motions are strongly influenced by local soil conditions. Reliable estimation of site effects is, therefore, crucial in order to avoid damage to infrastructures and mitigate other losses. Traditional geophysical exploration techniques are restricted in urban environments due to the presence of anthropogenic noises causing low seismic signal‐to‐noise ratio and other logistical issues. These problems are even more critical when the maximum investigation depth extends to hundreds of metres. The city of Girona, located in northeastern Spain, has seismic hazard represented by a peak ground acceleration value of 0.08 g for a return period of 500 years. The city was built at the confluence of four rivers, generating a complex surface geology with bedrock outcrops and the presence of stiff soils, soft soils, and also a volcanic basalt layer. This paper presents the results of the geophysical work, which was carried out in order to characterise the soil layers present in the urban area of Girona. All information obtained in this research will be useful in computing the amplification of ground motion and to perform microzonation studies. We have obtained the shear‐wave velocity profile in the study area using a combination of seismic noise array and multichannel analysis of surface waves techniques. Using the horizontal‐to‐vertical spectral ratio method, we have obtained the soil fundamental frequency. The combination of shear‐wave velocity and values of soil fundamental frequency provides a complete map of the bedrock topography. The expected velocity inversion due to the presence of shallow basalt flow has been targeted. Electrical resistivity tomography is found to be suitable to define the volcanic basalt thickness. This thickness value is used to constrain the inversion of surface wave dispersion curves and reduce shear‐wave velocity uncertainty. The new methodology overcomes the limitations that are typical to urban conditions and other geological complexities.

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V_{s}

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Geophysical measurements for site effects characterisation in the urban area of Girona, Spain

Macau

Benjumea

Gabàs

et al. 2018

Near Surface Geophysics

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“…If more impedance contrasts are present, the HVSR curve will show as many peaks, whose amplitude is linked to the corresponding impedance contrast. In the latter case, linking the experimental HVSR curves to the layered subsurface requires a modelling algorithm (Tsai and Housner, ; Sánchez‐Sesma et al , ; Lunedei and Albarello, , ), to predict the elastic propagation of waves in the subsurface, coupled with an inversion algorithm of the HVSR curves (Castellaro et al , ; Herak, ; Priolo et al ., ; Abu‐Zeid et al ., ; Mantovani et al , ; Bignardi et al , ). The mathematical treatment of the data is facilitated by the availability of open‐source and user‐friendly codes.…”

Section: Methods and Measurementsmentioning

confidence: 99%

“…discontinuity or physical surface) is retrieved by an inversion procedure, as explained earlier. Unfortunately, available inversion algorithms give poor results for frequencies higher than 10 Hz, because the inversion would be dominated by the seismic signature of deep features below the measuring point: this can be easily verified by performing a few tests with the popular, free inversion codes (Herak, ; Bignardi et al, ). Moreover, any inversion procedure is inherently ambiguous, because of the ratio present in the right term of Equation , so that a strong equivalence issue may arise.…”

Section: Methods and Measurementsmentioning

confidence: 99%

“…This method is based on the evaluation of the resonance frequencies due to the presence of layers with increasing acoustic impedance. Therefore, the rationale for using HVSR in a dense acquisition grid at the Pilastri site is primarily the assumption that the paleo‐surfaces were stiffened due to trampling of human activity over centuries of occupation and secondly, the HVSR is able to map subsurface elastic variations spanned on short distances (Aki and Richards, ; Bignardi et al , ; Bignardi et al , ), hence allowing to capture such variations by acquiring data over a dense grid of points whose dimensions can be regulated in accordance with the hypothesized spatial extent of these paleo‐surfaces. Moreover, the HVSR data acquisition technique may be carried out by just one operator.…”

Section: Introductionmentioning

confidence: 99%

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The Passive Seismic Technique ‘HVSR’ as a Reconnaissance Tool for Mapping Paleo‐soils: The Case of the Pilastri Archaeological Site, Northern Italy

Zeid

Corradini

Bignardi

et al. 2017

Archaeological Prospection

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Horizontal-to-vertical spectral ratio (HVSR) is a widely used geophysical technique in seismic microzonation studies. It is based on a specific analysis of seismic ambient noise. The method allows to obtain the frequency and amplitude of the resonance peaks of a layered earth with increasing acoustic impedance contrasts. The peaks can be interpreted to obtain an estimation of depth(s) of the impedance contrast horizon(s). Based on the assumption that long-term human trampling results in sediment's stiffening, which increased both density and velocity of seismic shear waves, the HVSR method was applied to investigate the shallow subsurface of an important, Middle Bronze Age, archaeological site called 'Pilastri Terramara' discovered at the end of the last century. Following recent excavations, archaeologists supposed that the settlement could extend outside the initially hypothesized borders, and decided to involve geophysicists to verify the truthiness of this new hypothesis and consequently to map the possible spatial extent of the paleo-surfaces frequented by ancient occupants. The purpose of the geophysical investigation was then to detect and possibly to map one or more anthropogenic paleo-surfaces over a relatively large area (about 12000 m 2 ). Unfortunately, direct evidences showed that the paleo-surfaces were embedded in clayey sediments and laying at depths ranging between 50 and 170 cm below ground level. Furthermore, the area to be investigated is occupied by a farm with glasshouses and other buildings. These obstacles constituted a real challenge that hindered the utilization of the most commonly used geophysical methods in archaeology, i.e. ground penetration radar (GPR), magnetometry and electrical resistivity tomography. For these reasons, we decided to use the HVSR method as a reconnaissance exploration tool, to confirm or rule out the presence of such paleo-surfaces. Spectral peaks related to acoustic horizons provided evidences about their presence and allowed to estimate their depths as was later confirmed by a new excavation.

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Ground vulnerability derived from the horizontal‐to‐vertical spectral ratio: Comparison with the damage distribution caused by the 2017 M_L 5.4 Pohang earthquake, Korea

Kang

Kim

Choi

et al. 2021

Near Surface Geophysics

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The city of Pohang in South Korea experienced substantial damage following the M L 5.4 earthquake on 15 November 2017. Damage surveys immediately after the earthquake revealed significant spatial variations in damage intensity across the epicentral area. We collected ambient noise data (three-component seismic data) from 124 locations in Pohang, covering a total area of 17 km × 20 km, and applied the horizontalto-vertical spectral ratio technique to estimate the resonance frequency, amplification factor and vulnerability of the ground to seismic shaking. Spatial variations exhibited by these three parameters are strongly correlated and consistent with variations in local geology. By comparing the distribution of the ground vulnerability index (Kg) with the damage distribution (or intensity) documented by the Korea Meteorological Administration following the earthquake, we confirm that the site effect is the prevailing effect that influences damage intensity in this region. We also demonstrate that Kg is an efficient proxy for identifying relatively fragile zones during ground shaking: in areas with a reported damage intensity of VIII, the proportion of the area with Kg > 20 is as high as 78.2%. Given that the study area has experienced a recent moderate earthquake, with significant economic consequences, our new results and analytical techniques will provide valuable information for future urbanization projects.

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OpenHVSR: imaging the subsurface 2D/3D elastic properties through multiple HVSR modeling and inversion

Cited by 86 publications

References 14 publications

Geophysical measurements for site effects characterisation in the urban area of Girona, Spain

Geophysical measurements for site effects characterisation in the urban area of Girona, Spain

The Passive Seismic Technique ‘HVSR’ as a Reconnaissance Tool for Mapping Paleo‐soils: The Case of the Pilastri Archaeological Site, Northern Italy

Ground vulnerability derived from the horizontal‐to‐vertical spectral ratio: Comparison with the damage distribution caused by the 2017 M_L 5.4 Pohang earthquake, Korea

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OpenHVSR: imaging the subsurface 2D/3D elastic properties through multiple HVSR modeling and inversion

Cited by 86 publications

References 14 publications

Geophysical measurements for site effects characterisation in the urban area of Girona, Spain

Geophysical measurements for site effects characterisation in the urban area of Girona, Spain

The Passive Seismic Technique ‘HVSR’ as a Reconnaissance Tool for Mapping Paleo‐soils: The Case of the Pilastri Archaeological Site, Northern Italy

Ground vulnerability derived from the horizontal‐to‐vertical spectral ratio: Comparison with the damage distribution caused by the 2017 ML 5.4 Pohang earthquake, Korea

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Product

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Ground vulnerability derived from the horizontal‐to‐vertical spectral ratio: Comparison with the damage distribution caused by the 2017 M_L 5.4 Pohang earthquake, Korea