Automated Large‐Scale Full Seismic Waveform Inversion for North America and the North Atlantic

Abstract

We present a new anisotropic seismic tomography model based on a multiscale full seismic waveform inversion for crustal and upper‐mantle structure from the western edge of North America across the North Atlantic and into Europe. The gradient‐based inversion strategy utilizes the adjoint state method coupled with an L‐BFGS quasi‐Newton optimization scheme. To improve the handling of large data quantities in the context of full seismic waveform inversions, we developed a workflow framework automating the procedure across all stages, enabling us to confidently invert for waveforms from 72 events recorded at 7,737 unique stations, resulting in a total of 144,693 raypaths, most of them with three‐component recordings. The final model after 20 iterations is able to explain complete waveforms including body as well as surface waves of earthquakes that were not used in the inversion down to periods of around 30 s. The model is complemented by a detailed resolution analysis in the form of 3‐D distributions of direction‐dependent resolution lengths.

Azimuthal Anisotropy of the North American Upper Mantle Based on Full Waveform Inversion

“…In addition, over the past decade, EarthScope deployed the USArray Transportable Array (TA) to cover the contiguous United States with a regular 70 km 70 km station grid, providing us unprecedented high‐quality and high‐density data for probing detailed seismic heterogeneities within the crust and mantle underneath North America. Earlier wave speed tomographic images of the North American crust and mantle have been significantly improved since the deployment of the USArray (Biryol et al, ; Burdick et al, ; Krischer et al, ; Moschetti et al, ; Obrebski et al, ; Schmandt & Humphreys, ; Schmandt & Lin, ; Porritt et al, ; Schaeffer & Lebedev, ; Yuan et al, ).…”

Seismic wavefield imaging of Earth’s interior across scales

“…Continentalscale imaging of Europe 91,[180][181][182][183][184][185][186][187] was spearheaded by the QUEST Initial Training Network in computational seismology, started in 2009. Subsequent studies focused on the construction of FWI-based models of North America 188,189 , Asia [190][191][192] and Antarctica 193 .…”

“…The FWI workflow (Fig. 2) is complex and prone to human errors and hardware failures, and automated recovery mechanisms are required at scale 189,[222][223][224] . Although 2D FWI can be carried out on a workstation or even a single graphics processing unit, the computational requirements for 3D (an)elastic FWI remain substantial because of the amount of data that needs to be analysed and the full 3D simulations of seismic-wave propagation that are required to calculate the synthetic seismograms and Fréchet derivatives of a misfit function.…”

Initial model assessment for intermediate-period full-waveform inversion of the contiguous U.S. and surrounding regions

“…Tomographic images of the Earth's interior, facilitated by large-aperture uniform array deployments (e.g., USArray in North America and CEArray in East Asia) have been tremendously improved in resolution of the crust and upper mantle structure (Yuan et al 2014;Chen et al 2015b;Shen & Ritzwoller 2016;Zhu et al 2017;Krischer et al 2018;Tao et al 2018). Meanwhile, advanced tomographic methods utilizing either multiple data sets (e.g., Shen & Ritzwoller (2016)) or full waveform inversion technique (e.g., Fichtner et al (2009Fichtner et al ( , 2010; Tape et al (2010); Lekić & Romanowicz (2011); Yuan et al (2014); Chen et al (2015aChen et al ( , 2017Chen et al ( , 2019; Zhu et al (2017); Tao et al (2018); Krischer et al (2018)) have helped remarkably in accurately rendering the physical properties of the crust and mantle structure. Although large-scale structures (on the order of thousands of kilometers) in tomographic models of the same regions extracted from different datasets and/or tomographic methods are similarly captured in general, the small-scale structures (on the order of hundreds and/or tens of kilometers) are still very different in terms of both the amplitude and the pattern of seismic wave speed anomalies.…”