Whole-mantle body-wave tomography under the hotspot of La Réunion

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The island of La Reunion is one of the most active and long-Iived volcanoes in the world. Its time- progressive, 5500-km long hotspot track emerges from the Deccan Traps of India, one of the largest flood basalt provinces on earth, which had a massive impact on global climate and life when they erupted. We want to establish the heat source and "plumbing system" that has been fueling this powerful hotspot for 65 million years. Through the RHUM-RUM project, a German- French effort funded mainly by the DFG and the ANR, we have deployed more than 90 broadband, ocean-bottom and Sand seismometers across the western Indian Ocean since 2011.The goal of RHUM-RUM is to seismically image a mantle plume - or lack of plume - from the surface down to the core-mantle boundary, and to understand the results in terms of material and heat flow. This comprises vertically ascending flow in the plume conduit, as well as any lateral flow spreading into the upper mantle of the western Indian Ocean. Here we are asking for funding for a Ph.D. Student to work the acquired waveform data into three-dimensional, whole-mantle P- and S-wave models of the mantle. We will be using multi-frequency tomography, a state-of-the art waveform Inversion method. Technical novelties or near-novelties include(i) the fully finite-frequency processing and Inversion of ocean-bottom and island seismograms across the entire usable frequency range of body waves.(ii) embedding of the RHUM-RUM data into a hemisphere-scale, whole-mantle model by joint Inversion with all other broadband data available for the hemisphere.(iii) the inclusion of core-diffracted waves, thanks to fully numerical waveform modeling. The goal is a significant improvement in structure of the lowermost mantle, the presumed footing region of deep mantle plumes.