Estimation of the Local Seismic Amplification on an Industrialized Site in the French Rhône Valley

Gelis, Céline; Cauchie, Léna; Cushing, Edward Marc; Froment, B.; Franco, S.; Jomard, Hervé; Moiriat, Denis; Provost, Ludmila; Sariguzel, B.; Tebib, Haifa

doi:10.1007/s00024-022-03069-x

Cited by 5 publications

(5 citation statements)

References 60 publications

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“…The Tricastin region (French Rhone Valley, Fig. 1a) is located on top of an elongated valley that was dug during the Messinian Salinity Crisis in Cretaceous sandstones and limestones and that is now filled with Pliocene and Quaternary sediments (sands and clays, Gélis et al 2022). The site is interesting to study for several reasons.…”

Section: Context Of the Studymentioning

confidence: 99%

“…Three nodes were co-located with three seismic stations (called ADHE, BOLL and PAUL, Fig. 1) that have been deployed intermittently since 2016-2017 and have therefore recorded the seismicity for several months (Gélis et al 2022). BOLL and PAUL sites are located on top of the sedimentary filling whereas ADHE is placed on top of the cretaceous outcrop.…”

Section: Data Acquisitionmentioning

confidence: 99%

“…BOLL and PAUL sites are located on top of the sedimentary filling whereas ADHE is placed on top of the cretaceous outcrop. Gélis et al (2022) showed almost flat H/V ratio with a value around 1 between 0.2 and 10 Hz at ADHE and therefore used this station as rock-reference for SSR computation.…”

Section: Data Acquisitionmentioning

confidence: 99%

“…40 is commonly chosen as the value of parameter b: this has been found to be a good compromise to efficiently smooth the spectra without oversmoothing. We benefit from SSR computed by Gélis et al (2022) at sites BOLL and PAUL relative to ADHE (following eq. 4) for comparison.…”

Section: Spectral Ratios Computationmentioning

confidence: 99%

“…4) for comparison. We invite the reader to refer to Gélis et al (2022) for details regarding the SSR computation. Using co-located nodes at BOLL and PAUL (see Section 2.2), we computed the SSRh at each sensor sx, either considering BOLL or PAUL as a local site reference (eq.…”

Section: Spectral Ratios Computationmentioning

confidence: 99%

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Insights into the conditions of application of noise-based spectral ratios in a highly industrialized area: a case study in the French Rhone Valley

Gisselbrecht

Froment

Boué

et al. 2023

Geophysical Journal International

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Summary The local ground motion amplification related to the geology at a specific site (i.e. the so-called site effects) may be classically quantified through the SSR (Standard Spectral Ratio) technique applied on earthquake recordings. However, such a quantification might be challenging to carry out in low-to-moderate seismicity regions. Methods based on background ambient noise, such as noise-based Standard Spectral Ratio (SSRn), might be of great interest in these areas. But noise-derived amplification is particularly sensitive to local anthropogenic sources, which may introduce biases in the evaluation of site effects by dominating the geological effects, especially for frequencies higher than 1 Hz. A hybrid approach (SSRh), developed to reduce biases in noise-based spectral ratios by combining classical earthquake-based spectral ratio (SSR) and SSRn, was recently introduced and relies on a site-reference. We here investigate the applicability of SSRn and SSRh in a heavily industrialized environment in the Tricastin Valley (South-East France), where critical facilities are located. We continuously recorded ambient noise from February to March 2020 on a 400-sensor seismic array covering an area of about 10 km by 10 km. We demonstrate that SSRn and SSRh computed below 1 Hz are able to reproduce amplification factors provided by SSR. By contrast, at frequencies higher than 1 Hz, SSRn strongly deviates from SSR. SSRh shows closer results to SSR but presents a dependence to the choice of the local site-reference, thereby questioning the possibility to use SSRh blindly to estimate the local amplification in our context. These discrepancies reflect the impact of local anthropogenic sources. We therefore introduced a two-step workflow to mitigate the influence of local sources. The first step is to define a characteristic time window to optimally isolate significant transient signals. The second step consists in selecting the time segments that do not contain these transients with a clustering-based approach. By applying this workflow, we were able to remove some strong anthropogenic transient signals likely to be generated by local sources at some sites and therefore to locally improve the amplification assessment through noise-based spectral ratios. However, stationary sources, whose impact cannot be removed through our procedure, remain a major issue. This study provides some insights into the application of SSRn and SSRh in noisy industrialized areas, especially regarding the impact of local noise sources. It illustrates the difficulty of having a procedure for mitigating the impact of these sources that is efficient everywhere inside such a complex anthropized environment, where different types of sources (including stationary sources) cohabit.

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Section: Context Of the Studymentioning

confidence: 99%

Section: Data Acquisitionmentioning

confidence: 99%

Section: Data Acquisitionmentioning

confidence: 99%

Section: Spectral Ratios Computationmentioning

confidence: 99%

Section: Spectral Ratios Computationmentioning

confidence: 99%

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Insights into the conditions of application of noise-based spectral ratios in a highly industrialized area: a case study in the French Rhone Valley

Gisselbrecht

Froment

Boué

et al. 2023

Geophysical Journal International

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Regional physics-based simulation of ground motion within the Rhȏne Valley, France, during the MW 4.9 2019 Le Teil earthquake

Smerzini

Vanini

Paolucci

et al. 2022

Bull Earthquake Eng

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In this paper, a comprehensive validation exercise of 3D physics-based numerical simulations (PBS) of seismic wave propagation is presented for a low-to-moderate seismicity area in the south east of France, within the Rhône River Valley, that hosts several operating nuclear installations. This area was hit on Nov 11, 2019, by an unusually damaging Mw 4.9 earthquake (Le Teil event). The numerical code SPEED ( http://speed.mox.polimi.it/ ), developed at Politecnico di Milano, Italy, was used to validate the simulations against the available recordings. When comparing simulations with records, a good to excellent agreement was found up to 8-10 Hz, showing that, even without a very detailed 3D numerical model of the medium, the PBS may provide realistic broadband predictions of earthquake ground motion. This also demonstrates that PBS, if suitably calibrated and validated, may be either an alternative or a useful complement to empirical ground motion models. Referring to the seismic risk evaluation of strategic and critical structures, infrastructures and industrial plants, such as nuclear power plants, the failure of which during an earthquake may endanger safety of population and cause environmental disasters, the 3D PBS may throw light on region-and site-specific features of ground shaking, especially in near-source conditions, that are typically poorly constrained in empirical models.

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Complementary Dense Datasets Acquired in a Low-to-Moderate Seismicity Area for Characterizing Site Effects: Application in the French Rhône Valley

Froment

Olivar-Castaño

Ohrnberger

et al. 2022

Seismological Research Letters

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Superficial geological layers can strongly modify the surface ground motion induced by an earthquake. These so-called site effects are highly variable from one site to another and still difficult to quantify for complex geological configurations. That is why site-specific studies can greatly contribute to improve the hazard prediction at a specific site. However, site-specific studies have historically been considered difficult to carry out in low-to-moderate seismicity regions. We present here seismological datasets acquired in the framework of the French–German dense array for seismic site effect estimation project in the heavily industrialized area surrounding the French Tricastin Nuclear Site (TNS). TNS is located above an ancient canyon dug by the Rhône River during the Messinian period. The strong lithological contrast between the sedimentary fill of the canyon and the substratum, as well as its expected confined geometry make this canyon a good candidate for generating site effects that are variable on short spatial scales. To investigate the impact of this geological structure on the seismic motion, we conducted complementary seismic campaigns in the area. The first main campaign consisted of deploying 400 nodes over a 10 × 10 km area for one month and aimed at recording the seismic ambient noise. A second seismic campaign involved the deployment of 49 broadband stations over the same area for more than eight months. This complementary campaign aimed at recording the seismicity (including local, regional, and teleseismic events). These different designs allowed us to target a variety of seismic data at different spatial and temporal scales. Beyond the interest for local operational seismic hazard applications, these datasets may be valuable for studying seismic wave propagation within complex kilometer-scale sedimentary structures. In this article, we present the deployment designs as well as initial analyses to provide information on the characteristics and the overall quality of the data acquired to future users.

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Estimation of the Local Seismic Amplification on an Industrialized Site in the French Rhône Valley

Cited by 5 publications

References 60 publications

Insights into the conditions of application of noise-based spectral ratios in a highly industrialized area: a case study in the French Rhone Valley

Insights into the conditions of application of noise-based spectral ratios in a highly industrialized area: a case study in the French Rhone Valley

Regional physics-based simulation of ground motion within the Rhȏne Valley, France, during the MW 4.9 2019 Le Teil earthquake

Complementary Dense Datasets Acquired in a Low-to-Moderate Seismicity Area for Characterizing Site Effects: Application in the French Rhône Valley

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