Anelastic Global Adjoint Tomography: Initial Results

Session: Full-Waveform Inversion: Recent Advances and Applications [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Attenuation, a measure of the energy loss of seismic waves, is a crucial parameter to constrain the partial melt, water content and thermal variations in the mantle. First-generation global adjoint tomography model GLAD-M15 (Bozdag et al. 2016) and its successor GLAD-M25 (Lei et al. in revision) are elastic models with transverse isotropy confined to the upper mantle constructed using the phase information of waveforms only. Our goal is to build a global anelastic upper-mantle mode by simultaneously inverting for elastic and anelastic parameters in adjoint inversions based on 3D wave simulations. We use both the phase and amplitudes of waveforms, which lead to exact global full-waveform inversion. Forward simulations of various 1D \& 3D elastic \& anelastic models suggest the necessity of simultaneous elastic/anelastic inversions as attenuation cause not only amplitude anomalies but also significant physical dispersion, particularly on surface waves. We apply a correction to source parameters (scalar moment and origin time) rather than inverting them simultaneously with the elastic and anelastic models to reduce the trade-off between parameters. We initiate simultaneous inversions using GLAD-M25 as the starting model and perform iterations with the dataset of 253 earthquakes used in the construction of GLAD-M15. The simulations are performed on Oak Ridge National Laboratory’s IBM AC922 Summit system. We initially use combined cross-correlation traveltime and amplitude measurements while investigating other misfit functions such as the instantaneous phase and envelope misfits. We will present our observations and results as well as future directions in global full-waveform inversions.

Presenting Author: Ridvan Orsvuran

Authors