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Bharadwaj, Pawan (author), Drijkoningen, G.G. (author), Mulder, W.A. (author), Tscharner, Thomas (author), Jenneskens, Rob (author)The Earth’s properties, composition and structure ahead of a tunnel boring machine (TBM) should be mapped for hazard assessment during excavation. We study the use of seismicexploration techniques for this purpose. We focus on a seismic system for soft soils, where shear waves are better and easier to interpret than compressional waves, as has...conference paper 2016
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Shamasundar, R. (author), Mulder, W.A. (author)The secondorder formulation of the wave equation is often used for spectralelement discretizations. For some applications, however, a firstorder formulation may be desirable. It can, in theory, provide much better accuracy in terms of numerical dispersion if the consistent mass matrix is used and the degree of the polynomial basis functions...conference paper 2016
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Shamasundara, R. (author), Mulder, W.A. (author)Finiteelement discretizations of the acoustic wave equation in the time domain often employ mass lumping to avoid the cost of inverting a large sparse mass matrix. For the secondorder formulation of the wave equation, mass lumping on Legendre–Gauss–Lobatto points does not harm the accuracy. Here, we consider a firstorder formulation of the...journal article 2016
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Mulder, W.A. (author), Shamasundara, R. (author)We consider isotropic elastic wave propagation with continuous masslumped finite elements on tetrahedra with explicit time stepping. These elements require higherorder polynomials in their interior to preserve accuracy after mass lumping and are only known up to degree 3. Global assembly of the symmetric stiffness matrix is a natural approach...journal article 2016
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Kadu, Ajinkya (author), van Leeuwen, Tristan (author), Mulder, W.A. (author)<br/>In seismic exploration, the delineation of large bodies with hard exterior contrasts but nearly constant interior properties is a challenge. Examples include salt diapirs, salt slabs, anhydrite or basalt layers. Salt geometries are of particular interest because they often have hydrocarbon reservoirs on their sides or underneath. This...conference paper 2016
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Shamasundar, R. (author), AlKhoury, R.I.N. (author), Mulder, W.A. (author)We investigated onedimensional numerical dispersion curves and error behaviour of four finiteelement schemes with polynomial basis functions: the standard elements with equidistant nodes, the LegendreGaussLobatto points, the ChebyshevGaussLobatto nodes without a weighting function and with. Mass lumping, required for efficiency reasons and...conference paper 2015
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Ponomarenko, A.V. (author), Kashtan, B.M. (author), Troyan, V.N. (author), Mulder, W.A. (author)We inverted seismic field data for a continuous, laterally invariant Pwave velocity profile. Instead of the usual approach that involves horizontal layers with piecewise constant densities and velocities, we consider models of one or two layers with a constant gradient of the squared slowness above a homogeneous halfspace. With a single layer...conference paper 2015
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Ishiyama, T. (author), Blacquiere, G. (author), Mulder, W.A. (author)3D seismic survey design provides an acquisition geometry for obtaining seismic data that enable imaging and amplitudeversusoffset applications of target reflectors with sufficient quality under given economical and operational constraints. However, in land or shallow water environments, surface waves are often dominant and will lower the...conference paper 2015
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Maas, P.J. (author), Grobbe, N. (author), Slob, E.C. (author), Mulder, W.A. (author)For multiparameter problems, such as the seismoelectric system, sensitivity analysis through resolution functions is a lowcost, fast method of determining whether measured fields are sensitive to certain subsurface parameters. We define a seismoelectric resolution function for the inversion of a bulk density perturbation. The synthetic data...conference paper 2015
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Kazei, V.V. (author), Kashtan, B.M. (author), Troyan, V.N. (author), Mulder, W.A. (author)Low frequencies play a crucial role in the convergence of fullwaveform inversion to the correct model in most of its current implementations. However, the lower the frequencies, the bigger are the amplitudes of the surface waves, causing the inversion to be driven by the latter. If they are not blanked out or removed, this may lead to...conference paper 2015
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Modave, A. (author), StCyr, A. (author), Warburton, T. (author), Mulder, W.A. (author)Improving both the accuracy and computational performance of simulation tools is a major challenge for seismic imaging, and generally requires specialized algorithms and computational implementations to make full use of modern hardware architectures. We present a computational strategy based on a highorder discontinuous Galerkin timedomain...conference paper 2015
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Rizzuti, G. (author), Mulder, W.A. (author)Efficient numerical wave modelling is essential for imaging methods such as reversetime migration (RTM) and full waveform inversion (FWI). In 2D, frequencydomain modelling with LU factorization as a direct solver can outperform timedomain methods by one order. For 3D problems, the computational complexity of the LU factorization as well as...conference paper 2015
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Pisupati, P.B. (author), Mulder, W.A. (author), Drijkoningen, G.G. (author)To overcome the local minima problem in FWI, we propose to use an auxiliary datadomain objective function during inversion. It reduces the data to a simpler form by squaring, followed by blurring to ensure that events that are too far apart can still interact during the inversion. As it effectively replaces seismic arrivals by bumps, we call it...conference paper 2015
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Pisupati, P.B. (author), Mulder, W.A. (author), Drijkoningen, G.G. (author), Reijnen, R. (author)In the nearsurface with unconsolidated soils, shear properties can be well imaged, sometimes better than Pwave properties. To facilitate ground prediction ahead of a tunnel boring machine (TBM), active ‘surveys’ with shearwave vibrators are carried out during boring. In such surveys, only a few shearwave vibrators can be placed in front of...conference paper 2015
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 Grobbe, N. (author), Maas, P. (author), Slob, E.C. (author), Mulder, W.A. (author) abstract 2015
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 Rizzuti, G. (author), Mulder, W.A. (author) conference paper 2014
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Pisupati, P.B. (author), Mulder, W.A. (author), Drijkoningen, G.G. (author)With singleparameter full waveform inversion, estimating the inverse of the Hessian matrix will accelerate the convergence, but is computationally expensive. Therefore, an approximate Hessian, which is easier to compute, is often used. Similarly, in the case of multiparameter full waveform inversion, the computation of the Hessian terms that...conference paper 2014
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Anikiev, D.V. (author), Kashtan, B.M. (author), Mulder, W.A. (author), Troyan, V.N. (author)An elastic isotropic medium is described with three parameters. In seismic migration the perturbation of one elastic parameter affects the images of all the three, which means that these parameters are coupled. For an effective quantitative reconstruction of the true elastic medium reflectivity one can apply an iterative linearized migration...journal article 2014
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Knibbe, H.P. (author), Mulder, W.A. (author), Oosterlee, C.W. (author), Vuik, C. (author)Threedimensional reversetime migration with the constantdensity acoustic wave equation requires an efficient numerical scheme for the computation of wavefields. An explicit finitedifference scheme in the time domain is a common choice. However, it requires a significant amount of disk space for the imaging condition. The frequencydomain...journal article 2014
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Mulder, W.A. (author)Masslumped continuous finite elements allow for explicit time stepping with the secondorder wave equation if the resulting integration weights are positive and provide sufficient accuracy. To meet these requirements on triangular and tetrahedral meshes, the construction of continuous finite elements for a given polynomial degree on the edges...journal article 2013