The Experts below are selected from a list of 16032 Experts worldwide ranked by ideXlab platform
P.y. Bard - One of the best experts on this subject based on the ideXlab platform.
-
Seismic Wave Propagation in Alluvial Basins and Influence of Site-City Interaction
Bulletin of the Seismological Society of America, 2008Co-Authors: Jean-françois Semblat, Marc Kham, P.y. BardAbstract: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 paper, the influence of surface structures on Seismic Wave Propagation is analyzed numerically in the case of an actual 2D shallow basin. At a local scale, the vibration of a surface structure can induce a Seismic Wavefield 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 Wavefield modification when compared to the free-field case. The coincidence between the fundamental frequencies of the soil layers and eigen frequencies of the surface structures is a key parameter to investigate site-city interaction. When comparing simplified site-city 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 Wavefield radiated by the city appears to be trapped within the alluvial basin and specific directivity features are found for this Wavefield. 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 (esp. city boundaries). These effects strongly depend on the urban configuration (city heterogeneity, building density, etc). Finally, the full characterization of the Seismic Wavefield 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 Wavefield radiated by the city.
-
Seismic-Wave Propagation in Alluvial Basins and Influence of Site-City Interaction
Bulletin of the Seismological Society of America, 2008Co-Authors: Jean-françois Semblat, Marc Kham, P.y. BardAbstract: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.
Jean-françois Semblat - One of the best experts on this subject based on the ideXlab platform.
-
Modeling Seismic Wave Propagation and amplification in 1D/2D/3D linear and nonlinear unbounded media
International Journal of Geomechanics, 2010Co-Authors: Jean-françois SemblatAbstract:To analyze Seismic Wave Propagation in geological structures, it is possible to consider various numerical approaches: the finite difference method, the spectral element method, the boundary element method, the finite element method, the finite volume method, etc. All these methods have various advantages and drawbacks. The amplification of Seismic Waves in surface soil layers is mainly due to the velocity contrast between these layers and, possibly, to topographic effects around crests and hills. The influence of the geometry of alluvial basins on the amplification process is also know to be large. Nevertheless, strong heterogeneities and complex geometries are not easy to take into account with all numerical methods. 2D/3D models are needed in many situations and the efficiency/accuracy of the numerical methods in such cases is in question. Furthermore, the radiation conditions at infinity are not easy to handle with finite differences or finite/spectral elements whereas it is explicitely accounted in the Boundary Element Method. Various absorbing layer methods (e.g. F-PML, M-PML) were recently proposed to attenuate the spurious Wave reflections especially in some difficult cases such as shallow numerical models or grazing incidences. Finally, strong earthquakes involve nonlinear effects in surficial soil layers. To model strong ground motion, it is thus necessary to consider the nonlinear dynamic behaviour of soils and simultaneously investigate Seismic Wave Propagation in complex 2D/3D geological structures! Recent advances in numerical formulations and constitutive models in such complex situations are presented and discussed in this paper. A crucial issue is the availability of the field/laboratory data to feed and validate such models.
-
Modeling Seismic Wave Propagation in 1D/2D/3D linear and nonlinear media
2008Co-Authors: Jean-françois SemblatAbstract:To analyze Seismic Wave Propagation in geological structures, it is possible to consider various numerical approaches: the finite difference method, the spectral element method, the boundary element method, the finite element method, the finite volume method, etc. All these methods have various advantages and drawbacks. The amplification of Seismic Waves in surface soil layers is mainly due to the velocity contrast between these layers and, possibly, to topographic effects around crests and hills. The influence of the geometry of alluvial basins on the amplification process is also know to be large. Nevertheless, strong heterogeneities and complex geometries are not easy to take into account with all numerical methods. 2D/3D models are needed in many situations and the efficiency/accuracy of the numerical methods in such cases is in question. Furthermore, strong earthquakes implies nonlinear effects in surficial soil layers. To model strong ground motion, it is then necessary to consider the nonlinear dynamic behaviour of soils and simultaneously investigate Seismic Wave Propagation in complex 2D/3D geometries ! Recent advances in numerical formulations and constitutive models in such complex situations are presented and discussed in this paper. Finally, a crucial point concerns the availability of the field/laboratory data to feed such models.
-
Seismic Wave Propagation in Alluvial Basins and Influence of Site-City Interaction
Bulletin of the Seismological Society of America, 2008Co-Authors: Jean-françois Semblat, Marc Kham, P.y. BardAbstract: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 paper, the influence of surface structures on Seismic Wave Propagation is analyzed numerically in the case of an actual 2D shallow basin. At a local scale, the vibration of a surface structure can induce a Seismic Wavefield 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 Wavefield modification when compared to the free-field case. The coincidence between the fundamental frequencies of the soil layers and eigen frequencies of the surface structures is a key parameter to investigate site-city interaction. When comparing simplified site-city 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 Wavefield radiated by the city appears to be trapped within the alluvial basin and specific directivity features are found for this Wavefield. 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 (esp. city boundaries). These effects strongly depend on the urban configuration (city heterogeneity, building density, etc). Finally, the full characterization of the Seismic Wavefield 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 Wavefield radiated by the city.
-
Seismic-Wave Propagation in Alluvial Basins and Influence of Site-City Interaction
Bulletin of the Seismological Society of America, 2008Co-Authors: Jean-françois Semblat, Marc Kham, P.y. BardAbstract: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.
Johan O. A. Robertsson - One of the best experts on this subject based on the ideXlab platform.
-
numerical modeling of Seismic Wave Propagation gridded two way Wave equation methods
GSW Books, 2012Co-Authors: Johan O. A. Robertsson, Kurt Nihei, Joakim O Blanch, Jeroen TrompAbstract:“Modeling of Seismic Wave Propagation is a core component in almost every aspect of exploration seismology, ranging from survey design methods to imaging and inversion algorithms. The last time SEG published a reprint volume on numerical modeling was in 1990. Since then, the last two decades has seen a step change in the application and use of Â"full Wave equationÂ" modeling methods enabled by the tremendous increase in available computational power. Full Waveform inversion, reverse time migration and 3D elastic finitedifference synthetic data generation are examples of modeling applications that are currently having a fundamental impact on our business. In Numerical Modeling of Seismic Wave Propagation: Gridded Two-way Wave-equation Methods, readers will find many of the wellknown and referenced papers from the exploration Seismic community as well as some of the key papers that have impacted other fields of seismology. Because the modeling literature is vast, we have limited the scope of the reprint volume to papers over the last two decades on modeling methods based on the full Wave equation. The reprint volume will be of particular interest to researchers and practitioners interested in modeling methods and their applications. The searchable CD includes the 114-page book of abstracts and the full papers.”
-
Numerical Modeling of Seismic Wave Propagation: Gridded Two-way Wave-equation Methods - Numerical modeling of Seismic Wave Propagation: Gridded Two-way Wave-equation Methods
2012Co-Authors: Johan O. A. Robertsson, Joakim O Blanch, Kurt T. Nihei, Jeroen TrompAbstract:“Modeling of Seismic Wave Propagation is a core component in almost every aspect of exploration seismology, ranging from survey design methods to imaging and inversion algorithms. The last time SEG published a reprint volume on numerical modeling was in 1990. Since then, the last two decades has seen a step change in the application and use of Â"full Wave equationÂ" modeling methods enabled by the tremendous increase in available computational power. Full Waveform inversion, reverse time migration and 3D elastic finitedifference synthetic data generation are examples of modeling applications that are currently having a fundamental impact on our business. In Numerical Modeling of Seismic Wave Propagation: Gridded Two-way Wave-equation Methods, readers will find many of the wellknown and referenced papers from the exploration Seismic community as well as some of the key papers that have impacted other fields of seismology. Because the modeling literature is vast, we have limited the scope of the reprint volume to papers over the last two decades on modeling methods based on the full Wave equation. The reprint volume will be of particular interest to researchers and practitioners interested in modeling methods and their applications. The searchable CD includes the 114-page book of abstracts and the full papers.”
-
the finite difference time domain method for modeling of Seismic Wave Propagation
Advances in Geophysics, 2007Co-Authors: Peter Moczo, Johan O. A. Robertsson, Leo EisnerAbstract:We present a review of the recent development in finite-difference time-domain modeling of Seismic Wave Propagation and earthquake motion. The finite-difference method is a robust numerical method applicable to structurally complex media. Due to its relative accuracy and computational efficiency it is the dominant method in modeling earthquake motion and it also is becoming increasingly more important in the Seismic industry and for structural modeling. We first introduce basic formulations and properties of the finite-difference schemes including promising recent advances. Then we address important topics as material discontinuities, realistic attenuation, anisotropy, the planar free surface boundary condition, free-surface topography, Wavefield excitation (including earthquake source dynamics), non-reflecting boundaries, and memory optimization and parallelization.
-
Modeling of Seismic Wave Propagation near the earth's surface
Physics of the Earth and Planetary Interiors, 1997Co-Authors: Johan O. A. Robertsson, Klaus HolligerAbstract:Abstract Realistic modeling of Seismic Wave Propagation in the vicinity of the earth's surface is complicated by large velocity contrasts, strong heterogeneity, severe attenuation, and topographic relief. To account for these complications, we employ a finite-difference solution of the 2D viscoelastic equations, a grid-refinement technique in the shallow parts of the model, and a generalized imaging condition to model free-surface topography. The grid-refinement approach allows us to vary the discretization of the model and the Wavefiedl with respect to the velocity structure. Compared to a standard uniform finite-difference grid approach, this saves considerable amount of memory and computations; thus enables modeling of Wave Propagation through large portions of the earth's crust. Moreover, the decreasing accuracy of the finite-difference method near the irregular free surface is compensated by using a finer grid-spacing in this region. Numerical tests show that the method is reliable and accurate. By applying this modeling technique to several canonical models of the near-surface region and upper crust, we find that scattering and mode conversions from topographic relief, Waveguide effects, and attenuation in the immediate subsurface tend to dominate the Seismic coda at near lapse times.
Klaus Holliger - One of the best experts on this subject based on the ideXlab platform.
-
Simulation of near-surface Seismic Wave Propagation in porous media
2010Co-Authors: Rolf Sidler, José M. Carcione, Klaus HolligerAbstract:We present a novel numerical algorithm for the simulation of poro-elastic Seismic Wave Propagation in general and for the accurate and realistic modeling of Scholte, Stoneley, and Rayleigh Waves in porous media in particular. The differential equations of motion are based on Biot’s theory of poro-elasticity and solved with a pseudo-spectral approach using Fourier and Chebyshev methods to compute the spatial derivatives along the horizontal and vertical directions, respectively. We stretch the mesh in the vertical direction to decrease the minimum grid spacing and reduce the computational cost. The free-surface boundary conditions are implemented with a characteristics approach, where the characteristics variables are evaluated at zero viscosity. The same procedure is used to model Seismic Wave Propagation at the interface between a fluid and porous medium. In this case, each medium is represented by a different mesh and the two meshes are combined through a domain-decomposition method. We simulate Seismic Wave Propagation with open and sealed boundary conditions and compare the numerical solution to an analytical solution obtained from the 2-D Green’s function. This algorithm represents a versatile and powerful basis for the poro-elastic analysis and interpretation of near-surface Seismic Wave Propagation phenomena in general and of Seismic surface-Wave-type data in particular.
-
Modeling of Seismic Wave Propagation near the earth's surface
Physics of the Earth and Planetary Interiors, 1997Co-Authors: Johan O. A. Robertsson, Klaus HolligerAbstract:Abstract Realistic modeling of Seismic Wave Propagation in the vicinity of the earth's surface is complicated by large velocity contrasts, strong heterogeneity, severe attenuation, and topographic relief. To account for these complications, we employ a finite-difference solution of the 2D viscoelastic equations, a grid-refinement technique in the shallow parts of the model, and a generalized imaging condition to model free-surface topography. The grid-refinement approach allows us to vary the discretization of the model and the Wavefiedl with respect to the velocity structure. Compared to a standard uniform finite-difference grid approach, this saves considerable amount of memory and computations; thus enables modeling of Wave Propagation through large portions of the earth's crust. Moreover, the decreasing accuracy of the finite-difference method near the irregular free surface is compensated by using a finer grid-spacing in this region. Numerical tests show that the method is reliable and accurate. By applying this modeling technique to several canonical models of the near-surface region and upper crust, we find that scattering and mode conversions from topographic relief, Waveguide effects, and attenuation in the immediate subsurface tend to dominate the Seismic coda at near lapse times.
Marc Kham - One of the best experts on this subject based on the ideXlab platform.
-
Seismic Wave Propagation in Alluvial Basins and Influence of Site-City Interaction
Bulletin of the Seismological Society of America, 2008Co-Authors: Jean-françois Semblat, Marc Kham, P.y. BardAbstract: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 paper, the influence of surface structures on Seismic Wave Propagation is analyzed numerically in the case of an actual 2D shallow basin. At a local scale, the vibration of a surface structure can induce a Seismic Wavefield 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 Wavefield modification when compared to the free-field case. The coincidence between the fundamental frequencies of the soil layers and eigen frequencies of the surface structures is a key parameter to investigate site-city interaction. When comparing simplified site-city 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 Wavefield radiated by the city appears to be trapped within the alluvial basin and specific directivity features are found for this Wavefield. 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 (esp. city boundaries). These effects strongly depend on the urban configuration (city heterogeneity, building density, etc). Finally, the full characterization of the Seismic Wavefield 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 Wavefield radiated by the city.
-
Seismic-Wave Propagation in Alluvial Basins and Influence of Site-City Interaction
Bulletin of the Seismological Society of America, 2008Co-Authors: Jean-françois Semblat, Marc Kham, P.y. BardAbstract: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.