We present an introduction to the spectral element method, which provides innovative numerical approach calculation of synthetic seismograms in 3-D earth models. The method combines flexibility a finite with accuracy method. One uses weak formulation equations motion, are solved on mesh hexahedral elements that is adapted free surface and main internal discontinuities model. wavefield discretized using high-degree Lagrange interpolants, integration over accomplished based upon...

Abstract We present the spectral element method to simulate elastic-wave propagation in realistic geological structures involving complieated free-surface topography and material interfaces for two- three-dimensional geometries. The introduced here is a high-order variational spatial approximation of equations. mass matrix diagonal by construction this method, which drastically reduces computational cost allows an efficient parallel implementation. Absorbing boundary conditions are form...

SUMMARY We use a spectral-element method to simulate seismic wave propagation throughout the entire globe. The is based upon weak formulation of equations motion and combines flexibility finite-element with accuracy global pseudospectral method. mesh honours all first- second-order discontinuities in earth model. To maintain relatively constant resolution model terms number grid points per wavelength, size elements increased depth conforming fashion, thus retaining diagonal mass matrix. In...

The perfectly matched layer (PML) absorbing boundary condition has proven to be very efficient from a numerical point of view for the elastic wave equation absorb both body waves with nongrazing incidence and surface waves. However, at grazing classical discrete PML method suffers large spurious reflections that make it less instance in case thin mesh slices, sources located close edge mesh, and/or receivers offset. We demonstrate how improve differential seismic based on an unsplit...

We simulate global seismic wave propagation based upon a spectral-element method. include the full complexity of 3-D Earth models, i.e. lateral variations in compressional-wave velocity, shear-wave velocity and density, crustal model, ellipticity, as well topography bathymetry. also effects oceans, rotation self-gravitation context Cowling approximation. For oceans we introduce formulation an equivalent load which do not need to be meshed explicitly. Some these effects, are often considered...

We use the spectral-element method to simulate ground motion generated by two recent and well-recorded small earthquakes in Los Angeles basin.Simulations are performed using a new sedimentary basin model that is constrained hundreds of petroleum-industry well logs more than 20,000 km seismic reflection profiles.The numerical simulations account for 3D variations seismicwave speeds density, topography bathymetry, attenuation.Simulations 9 September 2001 M w 4.2 Hollywood earthquake 3 2002...

The perfectly matched layer absorbing boundary condition has proven to be very efficient for the elastic wave equation written as a first-order system in velocity and stress. We demonstrate how use this same second-order displacement. This facilitates context of numerical schemes based upon such system, e.g. finite-element method, spectral-element method some finite-difference methods. illustrate efficiency 2-D benchmarks with body surface waves.

We present forward and adjoint spectral-element simulations of coupled acoustic (an)elastic seismic wave propagation on fully unstructured hexahedral meshes. Simulations benefit from recent advances in meshing, load balancing software optimization. Meshing may be accomplished using a mesh generation tool kit such as CUBIT, is facilitated by graph partitioning based the SCOTCH library. Coupling between fluid solid regions incorporated straightforward fashion domain decomposition. Topography,...

Large scientific applications deployed on current petascale systems expend a significant amount of their execution time dumping checkpoint files to remote storage. New fault tolerant techniques will be critical efficiently exploit post-petascale systems. In this work, we propose low-overhead high-frequency multi-level technique in which integrate highly-reliable topology-aware Reed-Solomon encoding three-level scheme. We hide the using one Fault-Tolerance dedicated thread per node. implement...

We present the first-generation global tomographic model constructed based on adjoint tomography, an iterative full-waveform inversion technique. Synthetic seismograms were calculated using GPU-accelerated spectral-element simulations of seismic wave propagation, accommodating effects due to 3-D anelastic crust & mantle structure, topography bathymetry, ocean load, ellipticity, rotation, and self-gravitation. Fréchet derivatives in models adjoint-state method. The performed Cray XK7 named...

SUMMARY Building on global adjoint tomography model GLAD-M15, we present transversely isotropic GLAD-M25, which is the result of 10 quasi-Newton tomographic iterations with an earthquake database consisting 1480 events in magnitude range 5.5 ≤ Mw 7.2, almost sixfold increase over first-generation model. We calculated fully 3-D synthetic seismograms a shortest period 17 s based GPU-accelerated spectral-element wave propagation solver accommodates effects due to anelastic crust and mantle...

The propagation of seismic waves through Earth can now be modeled accurately with the recently developed spectral-element method. This method takes into account heterogeneity in models, such as three-dimensional variations wave velocity, density, and crustal thickness. is implemented on relatively inexpensive clusters personal computers, so-called Beowulf machines. combination hardware software enables us to simulate broadband seismograms without intrinsic restrictions level or frequency content.

We introduce a spectral‐element method for modeling wave propagation in media with both fluid (acoustic) and solid (elastic) regions, as instance offshore seismic experiments. The problem is formulated terms of displacement elastic regions velocity potential acoustic regions. Matching between domains implemented based upon an interface integral the framework explicit prediction‐multicorrection staggered time scheme. formulation results mass matrix that diagonal by construction. scheme...

A spectral element method for the approximate solution of linear elastodynamic equations, set in a weak form, is shown to provide an efficient tool simulating elastic wave propagation realistic geological structures two- and three-dimensional geometries. The computational domain discretized into quadrangles, or hexahedra, defined with respect reference unit by invertible local mapping. Inside each element, numerical integration based on tensor-product Gauss–Lobatto–Legendre 1-D quadrature...

We introduce a numerical approach for modeling elastic wave propagation in 2-D and 3-D fully anisotropic media based upon spectral element method. The technique solves weak formulation of the equation, which is discretized using high‐order polynomial representation on finite mesh. For isotropic media, method known its high degree accuracy, ability to handle complex model geometries, low computational cost. show that can be extended media. mass matrix obtained diagonal by construction, leads...

We describe and present results from a finite-volume (FV) parallel computer code for forward modelling the Maxwell viscoelastic response of 3-D, self-gravitating, elastically compressible Earth to an arbitrary surface load. implement conservative, control volume discretization governing equations using tetrahedral grid in Cartesian geometry low-order, linear interpolation. The basic starting honours all major radial discontinuities Preliminary Reference Model (PREM), models are permitted...

Topography influences ground motion and, in general, increases the amplitude of shaking at mountain tops and ridges, whereas valleys have reduced motions, as is observed from data recorded during after real earthquakes numerical simulations.However, recent publications focused mainly on implications for mountainous regions themselves, impact surrounding low-lying areas has received less attention.Here, we develop a new spectral-element mesh implementation to accommodate realistic topography...

We accelerate a 3-D finite-difference in the time domain wave propagation code by factor between about 20 and 60 compared to serial implementation using graphics processing unit computing on NVIDIA cards with CUDA programming language. describe of simulate seismic waves heterogeneous elastic medium. also implement convolution perfectly matched layers efficiently absorb outgoing fictitious edges grid. show that runs card gives expected results comparing our those obtained running same...

In the context of simulation wave propagation, perfectly matched layer (PML) absorbing boundary has proven to be efficient absorb non-grazing incidence waves. However, classical discrete PML cannot efficiently waves reaching at grazing incidence. This is observed, for instance, in case thin mesh slices, or sources located close boundaries receivers large offset. order improve efficiency we derive an unsplit convolutional (CPML) a fourth-order staggered finite-difference numerical scheme...

We combine light detection and ranging (LiDAR) digital terrain model (DTM) data an improved mesh implementation to investigate the effects of highresolution surface topography on seismic ground motion based upon spectralelement method.In general, increases amplitude shaking at mountain tops ridges, whereas valleys usually have reduced motion, as has been observed in both records from past earthquakes numerical simulations.However, realistic not often clearly characterized simulations,...

The perfectly matched layer (PML) absorbing technique has become popular in numerical modeling elastic or poroelastic media because of its efficiency waves at nongrazing incidence. However, after discretization, grazing incidence, large spurious oscillations are sent back from the PML into main domain. then becomes less efficient when sources located close to edge truncated physical domain under study, for thin slices receivers a offset. We develop improved incidence wave equation based on...