UPFLOW 3-D mantle tomography from crust to core

As part of the ERC (European Research Council)-funded UPFLOW project (2021–2027), we conducted the largest passive seafoor seismic experiment to date in the Atlantic, focusing on the Azores-Madeira-Canary Islands region, a unique setting with multiple unresolved upwellings. Between June 2021 and August 2022, we deployed 50 and recovered 49 ocean bottom seismometers (OBSs) across a ~1,000×2,000 area with ~110–160 km spacing. The data reveal a wealth of good quality seismic signals, enabling detailed imaging of mantle upwellings and opening avenues for interdisciplinary research in marine biology and oceanography.

We present our ongoing UPFLOW 3-D mantle model series, which uses a combination of massive global seismic datasets (millions of body wave travel-times, multimode surface wave dispersion data) with tens of thousands of measurements from UPFLOW's OBS waveforms. Various modelling approaches are used ranging from computationally efficient ray theory-based global inversions to finite-frequency and waveform approaches. We invert for a range of model parameters including shear- and P-wave speed, as well as for radial anisotropy.

Our images show complex 3-D structures from the upper mantle to the lowermost mantle. We also observe lateral links between low velocity anomalies beneath the Canary, Azores and Madeira Islands associated with positive radial anisotropy anomalies, which possibly indicate plume ponding and horizontal mantle flow. Moreover, low-velocity anomalies right beneath the Azores appear not to extend into the lower mantle; instead, they seem to spread laterally and connect to the lower mantle beneath the center of our study region. We discuss the resolution of our images and well as their scope and geodynamical implications.