Abstract
AbstractLarge numbers of earthquakes occur in subduction zones that are marked by dipping, narrow high seismic velocity slabs. The existence of these fast velocity slabs can cause serious earthquake mislocation problems that can bias estimates of seismic travel time residuals. This can affect the recovery of subducting slabs in tomography as well as introduce significant artifacts into lower mantle structure in tomography models. In order to better account for known subducting slabs, we performed a new P and S wave joint tomography inversion incorporating a three‐dimensional thermal model of subducting slabs in the starting model. In addition, velocity and source locations were inverted for simultaneously. Our new P and S models feature higher‐amplitude subducting slabs compared with previous global tomography results. The S to P heterogeneity ratio based on the new tomography model indicates that thermal elastic effects alone cannot explain all the heterogeneities in the lower mantle. Much of the observed abnormal S to P heterogeneity ratio can be explained by anelastic effects, the spin transition, and phase transitions of bridgmanite to post‐perovskite in the lower mantle.
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