A complexity-driven framework for waveform tomography with discrete adjoints

Szenicer, Alexandre; Leng, Kuangdai; Nissen‐Meyer, Tarje

doi:10.1093/gji/ggaa349

Cited by 5 publications

(4 citation statements)

References 58 publications

(80 reference statements)

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“…Even though the adjoint wavefield computed on the wavefield-adapted mesh has no intuitive interpretation, it still yields the correct misfit gradient. Along similar lines, Szenicer et al (2020) developed off-axis sources for AxiSEM3D which allows for adjoint computations within that framework.…”

Section: Adjoint Modellingmentioning

confidence: 99%

Data-adaptive global full-waveform inversion

Thrastarson

Herwaarden

Krischer

et al. 2022

Geophysical Journal International

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Summary We present a novel approach to global-scale full-waveform inversion (FWI) that can reduce computational cost by over an order of magnitude, compared to previously published methods, without sacrificing physical and mathematical rigor. This is based on data-adaptation, and thereby application-oriented specialization, on two complementary levels. On the simulation level, we exploit the approximate azimuthal symmetry of seismic wavefields by implementing wavefield-adapted meshes and discrete adjoints, thereby lowering numerical simulation cost. On the measurement level, we employ a quasi-stochastic approach where variable mini-batches of data are used during an iterative misfit minimisation in order to promote a parsimonious exploitation of data. In addition to the methodological developments, we present an inversion of long-period (100 - 200 s) seismic waveforms from 1179 earthquakes for 3-D whole-mantle structure. The computational cost of the 72 iterations in the inversion approximately equals one third of a single iteration using an FWI approach with widely-used cubed-sphere-based meshes and non-stochastic gradient optimization. The resulting LOng-Wavelength Earth model (LOWE) constitutes the first global FWI constructed entirely from a spherically symmetric initial mantle structure. While mostly serving as a showcase for the method, LOWE contains a wealth of regional-scale structures that compare well to earlier tomographic images. Being conservatively smooth and based on minimal assumptions, it may therefore serve as starting model for future inversions at shorter period or smaller scales.

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Section: Adjoint Modellingmentioning

confidence: 99%

Data-adaptive global full-waveform inversion

Thrastarson

Herwaarden

Krischer

et al. 2022

Geophysical Journal International

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“…Testing for this specific threshold is beyond the scope of this study. We estimated the Fourier orders needed if we were to extend our 2.5D simulation to 3D based on Equation (5) in Szenicer et al (2020), and found 3D simulations are well out of reach given our available computational resources.…”

Section: Computational Methods and Its Enhancementsmentioning

confidence: 99%

Numerical and observational study of Sn-to-Lg conversion due to crustal-thickening: implications for identification of continental mantle earthquakes

Wang,

Klemperer

2024

Preprint

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We study Sn-to-Lg conversion at regional distances due to significant crustal thickening, particularly in the context of using Sn and Lg amplitude ratios (Sn/Lg) to identify continental mantle earthquakes. We further enhance recent developments in computational seismology to perform 2.5D simulations up to 5 Hz and 2,000 km. Our simulations compare propagation in a reference, constant-thickness crust from a source at three depths straddling the Moho, to 48 models of the same three sources propagating through Moho ramps of four different widths (dips) at four different distances from the source. We compare our synthetics to data from 12 earthquakes recorded on the HiCLIMB array across Tibet, of which six events from northwestern Tibet traverse no major crustal-thickness variation, and six located south of the Himalaya cross a major Moho ramp. Our observations on real data show that amplitude perturbations on individual Sn and Lg waves are smooth and mostly limited to near the ramp end. Even the more-pronounced amplitude variations seen in our simulations show that Sn/Lg for mid-crustal earthquakes is consistently lower than those for mantle earthquakes. Hence we can directly compare Sn/Lg for ramp-crossing and non-ramp-crossing earthquakes and identify new mantle earthquakes in northern India. Sn-to-Lg converted waves may be readily detected near the Moho ramp end through an enhancement in high-frequency content. In addition, we observe higher frequency content in Lg from crustal than from mantle earthquakes, which offers a new discriminant for continental mantle earthquakes based on frequency content of Lg waves alone.

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“…• Szenicer et al (2020): A complexity-driven framework for waveform tomography with discrete adjoints.…”

Section: Literaturementioning

confidence: 99%

AxiSEM3D - an introduction to using the code and its applications

Fernando,

Wolf,

Leng

et al. 2024

Preprint

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Welcome to the wonderful world of AxiSEM3D, a flexible, high-performance computational method for solving the elastodynamic wave equation in three-dimensional, hetereogeneous media. It has been used in seismology for the Earth, the Sun, the Moon, and many of other rocky planets and moons of the Solar System. In this manual, we will explore the practicalities of using this code, touching on the mathematical aspects as relevant to the casual user, the input and output files, and pre- and post-processing. This guide is not a replacement for any of the AxiSEM3D papers, which you will find listed in the next section. Nor does it go into any detail about how to install, build, configure, or make the code as these are dealt with in a separate installation guide. However, it does contain everything to do with the scientific aspects of the code and the user interface post-installation.

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A complexity-driven framework for waveform tomography with discrete adjoints

Cited by 5 publications

References 58 publications

Data-adaptive global full-waveform inversion

Data-adaptive global full-waveform inversion

Numerical and observational study of Sn-to-Lg conversion due to crustal-thickening: implications for identification of continental mantle earthquakes

AxiSEM3D - an introduction to using the code and its applications

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