Luca Lenti

Centre d'Études et d'Expertise sur les Risques, l'Environnement, la Mobilité et l'Aménagement

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Salvatore Martino

Sapienza University of Rome

Jean-François Semblat

Institut des Sciences de la Mécanique et Applications Industrielles

Antonella Paciello

National Agency for New Technologies, Energy and Sustainable Economic Development

Maria Paola Santisi d’Avila

Polytech Lille

Francesca Bozzano

Sapienza University of Rome

Roberto Iannucci

Sapienza University of Rome

Alberto Prestininzi

Sapienza University of Rome

J. Delgado

University of Alicante

Gabriele Scarascia Mugnozza

Sapienza University of Rome

Stefano Rivellino

Sapienza University of Rome

Cooperative Institutions

Sapienza University of Rome

Université Gustave Eiffel

Centre National de la Recherche Scientifique

Institute of Seismology

Terra

Institute for Economic Research on Firms and Growth

University of Alicante

University of Urbino

Universidad de Granada

Paris-Est Sup

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Modelling strong seismic ground motion: three-dimensional loading path versus wavefield polarization

Geophysical Journal International (2012)

Maria Paola Santisi d’Avila Luca Lenti Jean-François Semblat

Seismic waves due to strong earthquakes propagating in surficial soil layers may both reduce soil stiffness and increase the energy dissipation into the soil. To investigate seismic wave amplification in such cases, past studies have been devoted to one-directional shear wave propagation in a soil column (1D-propagation) considering one motion component only (1C-polarization). Three independent purely 1C computations may be performed ('1D-1C' approach) and directly superimposed in the case of weak motions (linear behaviour). This research aims at studying local site effects by considering seismic wave propagation in a 1-D soil profile accounting for the influence of the 3-D loading path and non-linear hysteretic behaviour of the soil. In the proposed '1D-3C' approach, the three components (3C-polarization) of the incident wave are simultaneously propagated into a horizontal multilayered soil. A 3-D non-linear constitutive relation for the soil is implemented in the framework of the Finite Element Method in the time domain. The complex rheology of soils is modelled by mean of a multisurface cyclic plasticity model of the Masing—Prandtl—Ishlinskii—Iwan type. The great advantage of this choice is that the only data needed to describe the model is the modulus reduction curve. A parametric study is carried out to characterize the changes in the seismic motion of the surficial layers due to both incident wavefield properties and soil non-linearities. The numerical simulations show a seismic response depending on several parameters such as polarization of seismic waves, material elastic and dynamic properties, as well as on the impedance contrast between layers and frequency content and oscillatory character of the input motion. The 3-D loading path due to the 3C-polarization leads to multi-axial stress interaction that reduces soil strength and increases non-linear effects. The non-linear behaviour of the soil may have beneficial or detrimental effects on the seismic response at the free surface, depending on the energy dissipation rate. Free surface time histories, stress–strain hysteresis loops and in-depth profiles of octahedral stress and strain are estimated for each soil column. The combination of three separate 1D-1C non-linear analyses is compared to the proposed 1D-3C approach, evidencing the influence of the 3C-polarization and the 3-D loading path on strong seismic motions.

Dispersive body waves

Shear waves

10.1111/j.1365-246x.2012.05599.x

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Strong Ground Motion in the 2011 Tohoku Earthquake: A One-Directional Three-Component Modeling

Bulletin of the Seismological Society of America (2013)

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 iscompared 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 3Cpolarization 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.

10.1785/0120120208

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Influence of the variability of soil profile properties on weak and strong seismic response

Soil Dynamics and Earthquake Engineering (2020)

Stefania Gobbi Luca Lenti Maria Paola Santisi d’Avila Jean-François Semblat Philippe Reiffsteck

Response analysis

Seismic risk

Soil horizon

10.1016/j.soildyn.2020.106200

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Citations (9)

Evidence of Two-Dimensional Amplification Effects in an Alluvial Valley (Valnerina, Italy) from Velocimetric Records and Numerical Models

Bulletin of the Seismological Society of America (2009)

Luca Lenti Salvatore Martino Antonella Paciello Gabriele Scarascia Mugnozza

Abstract The results of field surveys, velocimetric records, and numerical models are reported with the goal of analyzing the local seismic response in a section of the Nera River alluvial valley in central Italy. Alluvial deposit geometry and dynamic properties were defined by geological and geophysical investigations. 2D amplification effects were pointed out by horizontal-to-vertical spectral ratios (HVSRs) as well as by horizontal-to-horizontal spectral ratios (HHSRs) to a reference station; HVSRs were derived from both noise and weak-motion records, while HHSRs were only computed from weak motions. Where travertine deposits are interlayered within the alluvia, 2D amplification effects are shown only by HHSRs. The observed amplifications: (1) consist of peaks of the amplification functions A ( f ) in the range 1–10 Hz, (2) generally correspond to two frequency ranges whose values mainly depend on the valley shaped ratio and on the local heterogenities of the alluvial deposits, and (3) can be regarded as due to a 1D resonance combined with lateral wave propagation. Numerical models via the finite difference method were performed by the Italian National Institute for Geophysics and Volcanology Web Interface for Seismological Application and by the Fast Lagrangian Analysis of Continua codes. The obtained results: (1) show a good agreement with HHSRs, (2) prove that some 2D amplification effects are constrained by both the shape ratio of the valley and the heterogeneity of the alluvial deposits, (3) reveal focalization effects within the alluvial deposits strictly related to the shape of the valley, and (4) allow the comparison of the A ( f ) functions in both linear and nonlinear dynamic behavior and the computation of the shear strains due to ground motion within the alluvial deposits.

10.1785/0120080219

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Citations (24)

The role of near-field interaction between seismic waves and slope on the triggering of a rockslide at Lorca (SE Spain)

Natural hazards and earth system sciences (2012)

Pedro Alfaro J. Delgado Francisco Juan García-Tortosa J. J. Giner Luca Lenti

Abstract. A ~1000 m3 rockslide occurred close to Lorca (SE Spain) during the main shock (Mw = 5.1) of the May 2011 seismic sequence. The location of the rockslide, within 10 km of the earthquake epicenter and along the southern slope of a valley in which similar geological conditions occur on both slopes of the valley, suggests a significant near-field effect due to local seismic response. This could be related to the specific interaction between the topography and the obliquely propagating seismic waves. A dynamic stress strain numerical model was constructed using the FLAC 7.0 finite difference code to back analyze the Lorca rockslide event and relate its occurrence to both the local seismic amplification and the interaction between seismic waves and local topography. The results indicate that only for seismic waves with incidence angles in the range 0°–50° are the occurred slope instabilities expected. These results do not significantly change when varying the values for either stiffness or strength parameters within the range of the experimental data.

Rockslide

Epicenter

Stress field

10.5194/nhess-12-3631-2012

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Citations (24)

Nanoseismic monitoring of gravity-induced slope instabilities for the risk management of an aqueduct infrastructure in Central Apennines (Italy)

Natural Hazards (2016)

Matteo Fiorucci Roberto Iannucci Luca Lenti Salvatore Martino Antonella Paciello

Natural hazard

Aqueduct

Geologic hazards

10.1007/s11069-016-2516-5

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Citations (16)

Widespread landslides induced by the Mw 5.1 earthquake of 11 May 2011 in Lorca, SE Spain

Engineering Geology (2012)

Pedro Alfaro J. Delgado Francisco Juan García-Tortosa Luca Lenti John A. Lopez

Strong ground motion

10.1016/j.enggeo.2012.04.002

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Citations (75)

Seismic Wave Amplification in 3D Alluvial Basins: Aggravation factors from Fast Multipole BEM Simulations

HAL (Le Centre pour la Communication Scientifique Directe) (2017)

Kristel Carolina Meza Fajardo Jean-François Semblat Stéphanie Chaillat Luca Lenti

In this work, we study seismic wave amplification in alluvial basins having 3D canonical geometries through the Fast Multipole Boundary Element Method in the frequency domain. We investigate how much 3D amplification differs from the 1D (horizontal layering) and the 2D cases. Considering synthetic incident wave-fields, we examine the relationships between the amplification level and the most relevant physical parameters of the problem (impedance contrast, 3D aspect ratio, vertical and oblique incidence of plane waves). The FMBEM results show that the most important parameters for wave amplification are the impedance contrast and equivalent shape ratio. Using these two parameters, we derive simple rules to compute the fundamental frequency for different 3D basin shapes and the corresponding 3D aggravation factor for 5% damping.Effects on amplification due to 3D basin asymmetry are also studied and incorporated in the derived rules.

Layering

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Modélisation physique et numérique des séismes : application sur stratigraphies réelles

HAL (Le Centre pour la Communication Scientifique Directe) (2014)

Alberto Bretschneider Sandra Escoffier Luca Lenti Jean-François Semblat

Le laboratoire ‘Seismes et Vibrations’ de l’IFSTTAR dispose d’une centrifugeuse geotechnique avec simulateur de seismes embarque. En geotechnique sismique, la modelisation physique en macro-gravite est un outil avance permettant notamment l’etude de la propagation des ondes sismiques dans les sols (en champ libre et en presence de structures) et l’evaluation du potentiel de liquefaction des sols. L’avantage de cet outil est de pouvoir mesurer, sur des configurations simples, des grandeurs physiques d’interet, directement dans les sols et sur les structures representees a l’echelle reduite en conditions controlees. Les donnees experimentales permettent la calibration, puis la validation, de modeles numeriques simples. La modelisation numerique est utilisee par la suite pour l’analyse de situations plus complexes. Une etude de propagation d’ondes sismiques sur quatre stratigraphies reelles, alliant modelisation physique et numerique, est presentee ici. Les stratigraphies, caracterisees par differentes alternances de couches de sable et d’argile satures, ont ete reconstruites a l’echelle reduite en utilisant des sols a parametres controles en termes de granulometrie, densite relative, saturation, proprietes statiques et dynamiques. Pour chaque configuration, trois signaux sismiques ont ete appliques a la base des modeles : un seisme reel, un signal sinusoidal, un signal multi-frequentiels equivalent. La reponse de chaque colonne de sol a ete enregistree au travers d’un reseau vertical d’accelerometres. La modelisation numerique a ete utilisee a deux echelles differentes : une premiere modelisation a l’echelle modele (echelle reduite) a considere les conditions experimentales en termes de lithologies, conditions aux limites, acceleration centrifuge (55g), contraction du temps et des distances; une deuxieme modelisation, a l’echelle prototype, a considere les conditions reelles en termes de propriete des sols, acceleration terrestre(1g), geometrie, duree et frequences prototypes (echelle 1:1). Cette etude experimentale et numerique de la propagation des ondes sismiques, a validee l'utilisation de la modelisation en centrifugeuse pour comprendre les effets d’un seisme sur stratigraphies reelles, afin de prevoir le risque associe a un site donne et d'etablir des strategies pour sa reduction.

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The High Damaging Mw 5.1 Lorca 2011 Earthquake: Possible Role of Local Seismic Amplification

Springer eBooks (2014)

Luca Lenti Salvatore Martino Juan Luís Soler-Llorens Carlos López Casado Pedro Jáuregui

Fault plane

10.1007/978-3-319-09048-1_215

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Citations (1)