Waveform anisotropy tomography of the Azores-Canary-Madeira mantle region using UPFLOW OBS data

The Azores-Canary-Madeira region has been a focal point of scientific investigation regarding the presence and characteristics of mantle plumes, but so far seismological studies of the region's mantle structure have been limited due to sparse seismic coverage.  
Global tomography models exhibit considerable discrepancies concerning the presence and morphology of a lateral connection between  the Azores and Canary plume systems in the mantle. Furthermore, few seismic studies have examined potential interactions between the region's lithosphere, plumes and the adjacent Mid-Atlantic Ridge. Related highly relevant topics include characterising the age-dependent variability in oceanic lithosphere thickness and illuminating lithospheric and sub-lithospheric seismic structure. To address these issues, it is crucial to not only image isotropic seismic wave speeds but also map seismic anisotropy, as it can provide unique constraints on lithospheric thickness, fabric, and ultimately mantle flow. We build a new radially anisotropic tomographic model of the Azores-Canary-Madeira region using the partitioned waveform inversion method. Ocean bottom seismometer data from the UPFLOW array are combined with seismic data from nearby land stations. Automated waveform fitting of surface waves between ~ 300 and ~16 s period is used to retrieve path average model perturbations. These perturbations are subsequently used to invert for 3-D radially anisotropic mantle structure with a regularized least squares inversion. Mantle flow is interpreted from the retrieved patterns in isotropic velocity and radial anisotropy, while depth-dependent trends in these parameters provide insights into the region's oceanic lithosphere thickness and on potential plume-ridge and plume-lithosphere interactions.