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Ruan, J. (author), Ghose, R. (author), Mulder, W.A. (author)Induced seismicity from a gasproducing region such as Groningen is believed to be caused by reservoir depletion due to longterm gas production. However, because of the complexity and uncertainty regarding the underground structure and composition, it is difficult to quantify the effect on induced seismicity due to gas production. Here we use...poster 2021
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Ruan, J. (author), Ghose, R. (author), Mulder, W.A. (author)Induced seismicity from a gasproducing region such as Groningen is believed to be caused by reservoir depletion due to longterm gas production. However, because of the complexity and uncertainty regarding the underground structure and composition, it is difficult to quantify the effect on induced seismicity due to gas production. Here we use...poster 2021
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Werthmüller, D. (author), Mulder, W.A. (author), Slob, E.C. (author)3D controlledsource electromagnetic data are often computed directly in the domain of interest, either in the frequency domain or in the time domain. Computing it in one domain and transforming it via a Fourier transform to the other domain is a viable alternative. It requires the evaluation of many responses in the computational domain if...journal article 2021
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 Ruan, J. (author), Ghose, R. (author), Mulder, W.A. (author) abstract 2020
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Mulder, W.A. (author)Simulations of wave propagation in the Earth usually require truncation of a larger domain to the region of interest to keep computational cost acceptable. This introduces artificial boundaries that should not generate reflected waves. Most existing boundary conditions are not able to completely suppress all the reflected energy, but suffice...journal article 2020
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Mulder, W.A. (author)The representation of a force or moment point source in a spectral finiteelement code for modelling elastic wave propagation becomes fundamentally different in degenerate cases where the source is located on the boundary of an element. This difference is related to the fact that the finiteelement basis functions are continuous across...journal article 2020
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Cupillard, Paul (author), Mulder, W.A. (author), Irakarama, Modeste (author), Mazuyer, Antoine (author), Anquez, Pierre (author)Within the last decade, nonperiodic homogenization proved to be an accurate upscaling method for computing smooth equivalent media of elastic models of the earth interior. Doing so, it reveals the seismic anisotropy induced by smallscale structures and it eases the numerical simulation of wave propagation in complex geological settings by...abstract 2019
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Mulder, W.A. (author), Geevers, S. (author), van der Vegt, J. (author)Masslumped finite elements on tetrahedra offer more flexibility than their counterpart on hexahedra for the simulation of seismic wave propagation, but there is no general recipe for their construction, unlike as with hexahedra. Earlier, we found new elements up to degree 4 that have significantly less nodes than previously known elements by...conference paper 2019
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Werthmüller, D. (author), Mulder, W.A. (author), Slob, E.C. (author)Controlledsource electromagnetic (CSEM) surveys are a common geophysical investigationtool in the search for, amongst other, groundwater, hydrocarbons, and minerals. The numerical modelling of CSEM data requires the solution of the Maxwell equations. These canbe simplified in the particular case of CSEM, as the frequencies used in surveys are...journal article 2019
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Geevers, S. (author), Mulder, W.A. (author), van der Vegt, J (author)We present a new accuracy condition for constructing masslumped elements. This condition is less restrictive than the one previously used and enabled us to construct new masslumped tetrahedral elements for 3D wave propagation modelling. The new degree2 and degree3 elements require significantly fewer nodes than previous versions and mass...abstract 2019
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Geevers, S. (author), Mulder, W.A. (author), van der Vegt, J.J.W. (author)We present new and efficient quadrature rules for computing the stiffness matrices of masslumped tetrahedral elements for wave propagation modeling. These quadrature rules allow for a more efficient implementation of the masslumped finite element method and can handle materials that are heterogeneous within the element without loss of the...journal article 2019
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Geevers, S. (author), Mulder, W.A. (author), van der Vegt, J. J.W. (author)We analyse the dispersion properties of two types of explicit finite element methods for modelling acoustic and elastic wave propagation on tetrahedral meshes, namely masslumped finite element methods and symmetric interior penalty discontinuous Galerkin methods, both combined with a suitable Lax–Wendroff time integration scheme. The...journal article 2018
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Mulder, W.A. (author)One way to deal with the storage problem for the forward source wavefield in reverse time migration and fullwaveform inversion is the reconstruction of that wavefield during reverse time stepping along with the receiver wavefield. Apart from the final states of the source wavefield, this requires a strip of boundary values for the whole time...journal article 2018
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Shamasundar, R. (author), Mulder, W.A. (author)Finite elements can, in some cases, outperform finitedifference methods for modelling wave propagation in complex geological models with topography. In the weak form of the finiteelement method, the delta function is a natural way to represent a point source. If, instead of the usual secondorder form, the firstorder form of the wave equation...journal article 2018
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Geevers, S. (author), Mulder, W.A. (author), van der Vegt, J.J.W. (author)Spectral elements with mass lumping allow for explicit time stepping and are therefore attractive for modelling seismic wave propagation. Their formulation on rectangular elements is straighforward, but for tetrahedra only elements up to degree 3 are known. To preserve accuracy after mass lumping, these elements require additional nodes that...conference paper 2018
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Geevers, S. (author), Mulder, W.A. (author), van der Vegt, J. J.W. (author)We present a new accuracy condition for the construction of continuous masslumped elements. This condition is less restrictive than the one currently used and enabled us to construct new masslumped tetrahedral elements of degrees 2 to 4. The new degree2 and degree3 tetrahedral elements require 15 and 32 nodes per element, respectively, while...journal article 2018
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Ponomarenko, A. V. (author), Kashtan, B. M. (author), Troyan, V. N. (author), Mulder, W.A. (author)Surface waves are often used to estimate a nearsurface shearvelocity profile. The inverse problem is solved for the locally onedimensional problem of a set of homogeneous horizontal elastic layers. The result is a set of shear velocities, one for each layer. To obtain a Pwave velocity profile, the Pguided waves should be included in the...journal article 2017
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Mulder, W.A. (author)The presence of topography poses a challenge for seismic modeling with finitedifference codes. The representation of topography by means of an air layer or vacuum often leads to a substantial loss of numerical accuracy. A suitable modification of the finitedifference weights near the free surface can decrease that error. An existing...journal article 2017
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Shamasundar, R. (author), Mulder, W.A. (author)For seismic modelling, imaging and inversion, finitedifference methods are still the workhorse of the industry despite their inability to meet the increasing demand for improved accuracy in subsurface imaging. Finiteelement methods offer better accuracy but at a higher computational cost. A stressvelocity formulation with linear elements and...conference paper 2017
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Mulder, W.A. (author)Storage of the source wavefield during reversetime migration and fullwaveform inversion can be avoided by reconstructing that wavefield during reversetime stepping along with the receiver wavefield. With absorbing boundary conditions, this requires the final states of the source wavefield and a strip of boundary values at all times. The width...conference paper 2017