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Abstract Regularization of seismic inversions has a strong imprint on tomographic images. We analyze recorded and spectral‐element S, Sdiff, and SS waveforms to evaluate the benefit of body‐wave amplitudes in global tomography. L‐curve analysis for S40RTS models with recorded and synthetic waveforms show that SS‐S traveltimes and SS/S amplitude ratios have minima within the same damping parameter range. SS/S ratios for S40RTS and model GLAD‐M25 show the trade‐off between scale‐length and strength of lowermost‐mantle heterogeneities. The recorded SS/Sdiff ratios are lower than predicted by 3D mantle models which may be explained by a decrease in the mean shear velocity by at the lowermost 200 km of the mantle. Our results suggest that SS/S amplitude measurements made with 3D waveforms can be used to constrain damping in linearized inversions, and amplitudes are essential for studying the size of heterogeneities. 

Abstract With the rise of data volume and computing power, seismological research requires more advanced skills in data processing, numerical methods, and parallel computing. We present the experience of conducting training workshops in various forms of delivery to support the adoption of large-scale high-performance computing (HPC) and cloud computing, advancing seismological research. The seismological foci were on earthquake source parameter estimation in catalogs, forward and adjoint wavefield simulations in 2D and 3D at local, regional, and global scales, earthquake dynamics, ambient noise seismology, and machine learning. This contribution describes the series of workshops delivered as part of research projects, the learning outcomes for participants, and lessons learned by the instructors. Our curriculum was grounded on open and reproducible science, large-scale scientific computing and data mining, and computing infrastructure (access and usage) for HPC and the cloud. We also describe the types of teaching materials that have proven beneficial to the instruction and the sustainability of the program. We propose guidelines to deliver future workshops on these topics. 

SUMMARY Improving the resolution of seismic anelastic models is critical for a better understanding of the Earth’s subsurface structure and dynamics. Seismic attenuation plays a crucial role in estimating water content, partial melting and temperature variations in the Earth’s crust and mantle. However, compared to seismic wave-speed models, seismic attenuation tomography models tend to be less resolved. This is due to the complexity of amplitude measurements and the challenge of isolating the effect of attenuation in the data from other parameters. Physical dispersion caused by attenuation also affects seismic wave speeds, and neglecting scattering/defocusing effects in classical anelastic models can lead to biased results. To overcome these challenges, it is essential to account for the full 3-D complexity of seismic wave propagation. Although various synthetic tests have been conducted to validate anelastic full-waveform inversion (FWI), there is still a lack of understanding regarding the trade-off between elastic and anelastic parameters, as well as the variable influence of different parameter classes on the data. In this context, we present a synthetic study to explore different strategies for global anelastic inversions. To assess the resolution and sensitivity for different misfit functions, we first perform mono-parameter inversions by inverting only for attenuation. Then, to study trade-offs between parameters and resolution, we test two different inversion strategies (simultaneous and sequential) to jointly constrain the elastic and anelastic parameters. We found that a sequential inversion strategy performs better for imaging attenuation than a simultaneous inversion. We also demonstrate the dominance of seismic wave speeds over attenuation, underscoring the importance of determining a good approximation of the Hessian matrix and suitable damping factors for each parameter class. 

High-resolution seismic images are essential to gain insights into tectonic and geodynamical processes and assess seismic hazards. We constructed a P-wave model, MEPT (Middle East P-wave Travel-time), of the upper mantle beneath the Middle East and the surrounding region, which has a complex tectonic and geological history embodying various plate boundaries such as spreading ridges, subduction, suture zones, and strike-slip faults causing destructive earthquakes, specifically in Iran, Caucasus and Anatolia, and active volcanism. We use data from the ISC-EHB bulletin and onset-time readings of first-arrival P waves from waveforms recorded in the Arabian Peninsula. The additional onset-time readings from the regional waveform data significantly improve the resolution of the structure underneath the Arabian Peninsula, clearly indicating the boundary between the Arabian platform and the Arabian shield down to about 300 km depth, highlighted by slow and fast wavespeed perturbations in the upper mantle. Consistent with previous studies, we observe the Arabian-Eurasian collision, the Red Sea rifting, the Hellenic Arc, and low-velocity anomalies beneath the lithosphere of the Red Sea and the west of the Arabian shield. Our model supports the connection of the slow wavespeed anomalies in the lithosphere along the Red Sea to the Afar plume and shows evidence for smaller mantle upwellings underneath the Arabian plate and Jordan.