Global adjoint tomography—model GLAD-M25. Issue 1 (21st May 2020)

• Record Type: Journal Article
• Authors: Lei, Wenjie; Ruan, Youyi; Bozdağ, Ebru; Peter, Daniel; Lefebvre, Matthieu; Komatitsch, Dimitri; Tromp, Jeroen; Hill, Judith; Podhorszki, Norbert; Pugmire, David
• Is Part Of: Geophysical journal international. Volume 223:Issue 1(2020)
• Page Start: 1
• Page End: 21
• Publication Date: 2020-05-21
• Subjects: Waveform inversion -- Computational seismology -- Seismic anisotropy -- Seismic tomography -- Wave propagation; Geophysics -- Periodicals; 550
• DOI: 10.1093/gji/ggaa253
• Languages: English
• ISSNs: 0956-540X

Abstract

SUMMARY: Building on global adjoint tomography model GLAD-M15, we present transversely isotropic global model GLAD-M25, which is the result of 10 quasi-Newton tomographic iterations with an earthquake database consisting of 1480 events in the magnitude range 5.5 ≤ M w ≤ 7.2, an almost sixfold increase over the first-generation model. We calculated fully 3-D synthetic seismograms with a shortest period of 17 s based on a GPU-accelerated spectral-element wave propagation solver which accommodates effects due to 3-D anelastic crust and mantle structure, topography and bathymetry, the ocean load, ellipticity, rotation and self-gravitation. We used an adjoint-state method to calculate Fréchet derivatives in 3-D anelastic Earth models facilitated by a parsimonious storage algorithm. The simulations were performed on the Cray XK7 'Titan' and the IBM Power 9 'Summit' at the Oak Ridge Leadership Computing Facility. We quantitatively evaluated GLAD-M25 by assessing misfit reductions and traveltime anomaly histograms in 12 measurement categories. We performed similar assessments for a held-out data set consisting of 360 earthquakes, with results comparable to the actual inversion. We highlight the new model for a variety of plumes and subduction zones.