The Imprint of Plumes on Waveforms Using Spectral-Element Method Synthetics

Abstract:

Numerous global-scale and regional-scale tomographic images of the Earth’s mantle contain continuous low-velocity anomalies. It remains uncertain whether these anomalies are due to plumes. Variable spatial resolution complicates the interpretation of tomographic images. It is also not clear that the perturbations of wave-fronts that have passed through narrow plume stems in the lower mantle are observable at Earth’s surface. Using new spectral-element method simulations of teleseismic waveforms we determine the interaction of body-waves with hypothetical shear velocity structures of plumes. Our models include numerical simulations of whole mantle plumes that form at the base of mantle and interact with the 660-km discontinuity. We use the latest experimental constraints to convert thermal and thermo-chemical anomalies into wave-speed perturbations. We compute delay times (the primary data in tomography) from waveform correlations and evaluate whether wave diffraction can be used to detect plumes.