Global Anelastic Waveform Tomography
Seismic Attenuation
Understanding the distribution of seismic attenuation in the mantle is important for: 1. Discriminating between chemical and thermal heterogeneity; 2. Interpreting models of elastic structure derived from data at different frequencies.
Yet, while mapping of the 3D elastic structure of the upper mantle has benefited from approximate first-order perturbation techniques, modeling of the 3D distribution of seismic attenuation has lagged behind due to difficulties in accounting for purely elastic effects of scattering at sharp interfaces and (de)focusing, which can obscure the anelastic signal.
Model SEMUCB-WMQ
Our most recent model uses the Spectral Element Method in the construction of a 3D upper mantle Q model which can be found here:[[1]]. The SEM is used forthe forward modeling part while finite-frequency kernels NACT is used in the inversion.
Model QRLW8
QRLW8 is an anelastic 3D model of the upper mantle from full seismogram waveform inversion developed by Yuancheng Gung, Barbara Romanowicz. Read more about the model, and the interesting implications it raises.
The figure below shows our most recent upper mantle Q model, QRLW8 (Gung and Romanowicz, 2004): 1. Derived from long period seismograms in the time domain, comprising both fundamental mode surface waves and overtones; 2. Used an iterative waveform inversion technique, in which we solve for elastic and anelastic structure in successive steps; 3. Employed non-linear asymptotic mode coupling theory as the theoretical framework for both the forward and inverse parts of our inversions (Romanowicz, 1987; Li and Romanowicz, 1996).
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