AxiSEM3D: broad-band seismic wavefields in 3-D global earth models with undulating discontinuities

Leng, Kuangdai; Nissen‐Meyer, Tarje; Driel, Martin van; Hosseini, Kasra; Al-Attar, David

doi:10.1093/gji/ggz092

Cited by 80 publications

(81 citation statements)

References 84 publications

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“…This figure shows snapshots of the displacement seismic wavefield at the CMB for both the PREM model and the same ULVZ model, as shown in Figure 2. Here, the seismic wavefield is computed with a dominant period of approximately 1 s using the AxiSEM3D technique [33,34]. Animations of these wavefield simulations are included as online supplements (Videos S1 and S2).…”

Section: Introductionmentioning

confidence: 99%

New Candidate Ultralow-Velocity Zone Locations from Highly Anomalous SPdKS Waveforms

et al. 2020

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Ultralow-velocity zones (ULVZs) at the core–mantle boundary (CMB) represent some of the most preternatural features in Earth’s mantle. These zones most likely contain partial melt, extremely high iron content ferropericlase, or combinations of both. We analyzed a new collection of 58,155 carefully processed and quality-controlled broadband recordings of the seismic phase SPdKS in the epicentral distance range from 106° to 115°. These data sample 56.9% of the CMB by surface area. From these recordings we searched for the most anomalous seismic waveforms that are indicative of ULVZ presence. We used a Bayesian approach to identify the regions of the CMB that have the highest probability of containing ULVZs, thereby identifying sixteen regions of interest. Of these regions, we corroborate well-known ULVZ existence beneath the South China Sea, southwest Pacific, the Samoa hotspot, the southwestern US/northern Mexico, and Iceland. We find good evidence for new ULVZs beneath North Africa, East Asia, and north of Papua New Guinea. We provide further evidence for ULVZs in regions where some evidence has been hinted at before beneath the Philippine Sea, the Pacific Northwest, and the Amazon Basin. Additional evidence is shown for potential ULVZs at the base of the Caroline, San Felix and Galapagos hotspots.

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Section: Introductionmentioning

confidence: 99%

New Candidate Ultralow-Velocity Zone Locations from Highly Anomalous SPdKS Waveforms

et al. 2020

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“…Leng et al [10,11] readily show that for a variety of current 3D models on the global scale seismic waves retain their azimuthal smoothness with respect to the source location, hence we do not dive into quantitative aspects of applicability, but illustrate the idea with simple 2D examples. To this end, we consider the membrane wave approximation of surface waves [e.g.…”

Section: Motivationmentioning

confidence: 94%

“…Leng et al [10] introduce an empirical relation for the azimuthal resolution as a function of depth and source distance for global wave propagation. Furthermore, Leng et al [11] monitor the energy in each azimuthal order as a function of depth and distance to the source to derive the required lateral resolution for a given 3D model and source.…”

Section: Anisotropic Adaptive Mesh Refinement (Aamr)mentioning

confidence: 99%

“…The work by Leng et al [10,11] suggests that a scheme adapted to the azimuthal complexity of the wavefield can be very beneficial for global wave propagation with speed-ups of up to three orders of magnitude. The aAMR technique can be employed on the global scale as shown in Fig.…”

Section: Mesh Constructionmentioning

confidence: 99%

“…In this way, it reduces the numerical problem to two dimensions. Recently, Leng et al [10,11] generalized this idea to include 3D variations of the elastic parameters as well as crustal thickness variations, topography and ocean loading by replacing the azimuthal analytical solution by a pseudo-spectral numerical approach and report speed-ups of up to several orders of magnitude for the case of global wave propagation in comparison to the 3D spectral-element method [SPECFEM3D_GLOBE,12]. These performance gains are based on the observation that the complexity of the wavefield emanating from a seismic source is high in the radial and vertical direction, but much lower in the azimuthal direction.…”

Section: Introductionmentioning

confidence: 99%

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Accelerating numerical wave-propagation using wavefield adapted meshes, Part I: Forward and adjoint modelling

Driel¹,

Boehm²,

Krischer³

et al. 2019

Preprint

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An order of magnitude speed-up in finite-element modelling of wave propagation can be achieved by adapting the mesh to the anticipated space-dependent complexity and smoothness of the waves. This can be achieved by designing the mesh not only to respect the local wavelengths, but also the propagation direction of the waves depending on the source location, hence by anisotropic adaptive mesh refinement. Discrete gradients with respect to material properties as needed in full waveform inversion can still be computed exactly, but at greatly reduced computational cost. In order to do this, we explicitly distinguish the discretization of the model space from the discretization of the wavefield and derive the necessary expressions to map the discrete gradient into the model space. While the idea is applicable to any wave propagation problem that retains predictable smoothness in the solution, we highlight the idea of this approach with instructive 2D examples of forward as well as inverse elastic wave propagation.Furthermore, we apply the method to 3D global seismic wave simulations and demonstrate how meshes can be constructed that take advantage of high-order mappings from the reference coordinates of the finite elements to physical coordinates. Error level and speed-ups are estimated based on convergence tests with 1D and 3D models.

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SASSIER22: Full-waveform tomography of the eastern Indonesian region that includes surface topography and the fluid ocean

Wehner

Rawlinson

Greenfield³

et al. 2022

Preprint

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We present a new 3-D seismic structural model of the eastern Indonesian region and its surroundings from full-waveform inversion (FWI) that exploits seismic data filtered at periods between 15 -150 s. SASSY21 -a recent 3-D FWI tomographic model of Southeast Asia -is used as a starting model, and our study region is characterized by particularly good data coverage, which facilitates a more refined image. We use the spectral-element solver Salvus to determine the full 3-D wavefield, accounting for the fluid ocean explicitly by solving a coupled system of acoustic and elastic wave equations. This is computationally more expensive but allows seismic waves within the water layer to be simulated, which becomes important for periods [?] 20 s. We investigate path-dependent effects of surface elevation (topography and bathymetry) and the fluid ocean on synthetic waveforms, and compare our final model to the tomographic result obtained with the frequently used ocean loading approximation. Furthermore, we highlight some of the key features of our final model -SASSIER22 -after 34 L-BFGS iterations, which reveals detailed anomalies down to the mantle transition zone, including a convergent double-subduction zone along the southern segment of the Philippine Trench, which was not evident in the starting model. A more detailed illumination of the slab beneath the North Sulawesi Trench reveals a pronounced positive wavespeed anomaly down to 200 km depth, consistent with the maximum depth of seismicity, and a more diffuse but aseismic positive wavespeed anomaly that continues to the 410 km discontinuity.

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AxiSEM3D: broad-band seismic wavefields in 3-D global earth models with undulating discontinuities

Cited by 80 publications

References 84 publications

New Candidate Ultralow-Velocity Zone Locations from Highly Anomalous SPdKS Waveforms

New Candidate Ultralow-Velocity Zone Locations from Highly Anomalous SPdKS Waveforms

Accelerating numerical wave-propagation using wavefield adapted meshes, Part I: Forward and adjoint modelling

SASSIER22: Full-waveform tomography of the eastern Indonesian region that includes surface topography and the fluid ocean

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