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Dive into the research topics where Jean François Semblat is active.

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Featured researches published by Jean François Semblat.


Bulletin of the Seismological Society of America | 2008

Seismic-Wave Propagation in Alluvial Basins and Influence of Site-City Interaction

Jean François Semblat; Marc Kham; Pierre Yves Bard

The geometrical and mechanical features of alluvial deposits have a major influence on seismic-wave propagation and amplification. However, for alluvial basins located in densely urbanized areas, the surface structures such as buildings could influence seismic-wave propagation near the free surface. In this article, the influence of surface structures on seismic-wave propagation is analyzed numerically in the case of an actual two-dimensional (2D) shallow basin. At a local scale, the vibration of a surface structure can induce a seismic wave field in the surficial soil layers. At the scale of an alluvial basin, the site-city models considered herein show that the city effect can lead to a significant seismic wave-field modification when compared to the free-field case. The coincidence between the fundamental frequencies of the soil layers and eigenfrequencies of the surface structures is a key parameter to investigate site-city interaction. When comparing simplified sitecity models (Kham et al., 2006) to the basin-city model, the influence of the lateral heterogeneities on the site-city interaction is found to be significant. Indeed, the seismic wave field radiated by the city appears to be trapped within the alluvial basin, and specific directivity features are found for this wave field. The influence of site-city interaction on the free-field seismic hazard may then be significant. The effects of the site-city interaction are beneficial in some parts of the city or detrimental in other parts (especially city boundaries). These effects strongly depend on the urban configuration (city heterogeneity, building density, etc.). Finally, the full characterization of the seismic wave field in densely urbanized areas could often raise the need for investigating site-city interaction and consider such parameters as basin and city fundamental frequencies, building density and city arrangement, as well as basin effects combined with the seismic wave field radiated by the city.


Bulletin of the Seismological Society of America | 2014

Influence of the Vs profiles beyond 30 m depth on linear site effects: assessment from the KiK-net data

Julie Régnier; Luis Fabian Bonilla; Etienne Bertrand; Jean François Semblat

Site effects may be assessed using a standard soil classification parameter, VS30 (the harmonic average shear-wave velocity in the first 30 m); however, this index does not account for the complexity of the velocity profile, especially its variability at depth. In the present study, in addition to VS30, we propose consideration of the gradient of the VS profile from 0 to 30 m depth, denoted B30. A lower gradient value means low velocity increases with depth; a higher gradient indicates a rapid velocity increase with depth in the shallow layers. In addition, we consider the fundamental resonance frequency of the soil (f0), which has been shown to be a relevant parameter for site-effect assessment and which is obtained from the empirical site response. Using the Japanese KiK-net database, we analyze the variability of the VS profiles and the empirical borehole site responses of selected sites through the VS30, the velocity gradient B30, and f0. We select 289 sites for which the 1D linear numerical modeling is close to the empirical site response and a VS at the downhole station is greater than 1000 m=s. For a given VS30 class, B30, and f0 can be used to distinguish between two types of sites: deep sedimentary sites and sites with high velocity contrast at shallow depths. We find that, even if the gradient is calculated using shallow information, its use improves the site amplification characterization, compared to using only VS30, by reducing the intersite site-response variability. As expected, however, this improvement is limited for deep sedimentary sites. On the other hand, f0 is able to reduce the intersite response variability for deep sedimentary sites even though it is limited to specific VS30 classes. Thus, the combined use of VS30, B30, and f0 improves the assessment of linear site amplification.


arXiv: Geophysics | 2013

Strong Ground Motion in the 2011 Tohoku Earthquake: a 1Directional - 3Component Modeling

Maria Paola Santisi d'Avila; Jean François Semblat; Luca Lenti

Local wave amplification due to strong seismic motions in surficial multilayered soil is influenced by several parameters such as the wavefield polarization and the dynamic properties and impedance contrast between soil layers. The present research aims at investigating seismic motion amplification in the 2011 Tohoku earthquake through a one-directional three-component (1D-3C) wave propagation model. A 3D nonlinear constitutive relation for dry soils under cyclic loading is implemented in a quadratic line finite element model. The soil rheology is modeled by mean of a multi-surface cyclic plasticity model of the Masing-Prandtl-Ishlinskii-Iwan (MPII) type. Its major advantage is that the rheology is characterized by few commonly measured parameters. Ground motions are computed at the surface of soil profiles in the Tohoku area (Japan) by propagating 3C signals recorded at rock outcrops, during the 2011 Tohoku earthquake. Computed surface ground motions are compared to the Tohoku earthquake records at alluvial sites and the reliability of the 1D-3C model is corroborated. The 1D-3C approach is compared with the combination of three separate one-directional analyses of one motion component propagated independently (1D-1C approach). The 3D loading path due to the 3C-polarization leads to multiaxial stress interaction that reduces soil strength and increases nonlinear effects. Time histories and spectral amplitudes, for the Tohoku earthquake, are numerically reproduced. The 1D-3C approach allows the evaluation of various parameters of the 3C motion and 3D stress and strain evolution all over the soil profile.


International Journal for Numerical Methods in Engineering | 2011

A simple multi‐directional absorbing layer method to simulate elastic wave propagation in unbounded domains

Jean François Semblat; Luca Lenti; Ali Gandomzadeh


Bulletin des laboratoires des ponts et chaussées | 2013

Modélisation numérique des effets de site sismiques par approches modale et propagative

Jean François Semblat; Marc Kham; Roberto Paolucci; Anne Marie Duval; Pierre Yves Bard


3e Congreso Nacional de Ingenieria Sismica | 2007

Seismic hazard in urban environments : Can man modify the hazard ?

Pierre Yves Bard; Philippe Gueguen; Jean Louis Chazelas; Marc Kham; Jean François Semblat


Archive | 2005

Site-city interaction. In : Assessing and managing earthquake risk

Pierre Yves Bard; Jean Louis Chazelas; Philippe Gueguen; Marc Kham; Jean François Semblat


Archive | 2015

Experimental and Numerical Investigations of Nonlinearity in Soils Using Advanced Laboratory-scaled Models (ENINALS project): from a site-test to a centrifuge model In: Experimental Research in Earthquake Engineering

Francesca Bozzano; Salvatore Martino; Alberto Prestininzi; Gabriele Scarascia Mugnozza; Luis Fabian Bonilla; Alberto Bretschneider; Jean Louis Chazelas; Sandra Escoffier; Luca Lenti; Jean François Semblat


Journées Nationales de Géotechnique et de Géologie de l’Ingénieur JNGG2014 | 2014

Modélisation physique et numérique des séismes : application sur stratigraphies réelles

Alberto Bretschneider; Sandra Escoffier; Luca Lenti; Jean François Semblat


Bulletin des Laboratoires des Ponts et Chaussées | 2013

Interaction Site-Ville : Approches expérimentales et numériques

Philippe Gueguen; Jean François Semblat; Pierre Yves Bard; Jean Louis Chazelas

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Marc Kham

Électricité de France

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Pierre Delage

École des ponts ParisTech

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