Source: Journal of Geophysical Research: Solid Earth
Though its usage is becoming increasingly commonplace, the method of adjoint tomography is challenging to implement due to complex workflows, large data sets, difficulties in visualization and computational costs.
Rodgers et al.  effectively leverage the comprehensive USArray dataset in the recovery of western United States crust and upper mantle velocity structure using adjoint tomography. Resulting 3D wavefield simulations of 72 regional earthquakes representing a total of over 94,000 three-component broadband waveforms display remarkable fidelity to observed seismograms, providing testament to the veracity of recovered structure.
The western U.S. 3D (WUS256) model presented here will likely serve as an important reference in future studies.
Citation: Rodgers, A., Krischer, L., Afanasiev, M., Boehm, C., Doody, C., Chiang, A., & Simmons, N. (2022). WUS256: An Adjoint Waveform Tomography Model of the Crust and Upper Mantle of the Western United States for Improved Waveform Simulations. Journal of Geophysical Research: Solid Earth, 127, e2022JB024549. https://doi.org/10.1029/2022JB024549
—Michael Bostock, Editor, Journal of Geophysical Research: Solid Earth