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Upper mantle seismic anisotropy around La Réunion hotspot and its surrounding mid-ocean ridges


IPGP - Îlot Cuvier


Soutenances de thèses


John-Robert Scholz

Sismologie (SIS)

The hotspot island of La Réunion is proposed to be fed by a deep-rooted mantle plume. I present new insights on upper mantle structures and dynamics around La Réunion and its neighboring mid-ocean ridges. My findings are based on the physical property of seismic anisotropy, assessed via measurements of splitting SKS-phases. I used records of land and ocean-bottom seismometers (OBS) deployed by the RHUM-RUM project. Milestones and key findings may be summarised as: - In a novel approach, I oriented the horizontal OBS components – an important pre-processing step. - Mantle flows beneath mid-ocean ridges may orient as a function of the ridges’ spreading rates. - Asthenosphere is flowing from beneath La Réunion towards the Central-Indian Ridge at 1000 km distance, supporting a 40 years old hypothesis. Almost the entire Central-Indian Ridge could be fed by multiple, asthenospheric flows sourcing beneath the Mascarene Basin where a large low-velocity anomaly at asthenospheric depths is observed.