Slab Tearing Underneath the Bransfield Strait, Antarctica Parera Portell, Joan Antoni Mancilla Pérez, Flor de Lis Almendros González, Francisco Javier Stich, Daniel We conduct a P-wave receiver function analysis of the Bransfield Strait (West Antarctica) to determine the lithospheric structure of this back-arc basin, thanks to 31 temporary and permanent stations. Our main finding is a 15 km tear of the Phoenix slab, coinciding with the location of the 2020–2021 Orca earthquake swarm's epicenters. Teleseismic wave modeling reveals that the two major earthquakes occurred at the base of the crust, suggesting that the swarm could have been triggered by active underplating driven by mantle flow through the slab tear. There is evidence for such an underplating layer at least under Deception Island and for a widespread low velocity zone in the mantle wedge probably undergoing partial melting. We found average crustal thickness (30.5 ± 1.0 km) and Vp/Vs (1.81 ± 0.04) values close to average extended continental crust, although results in the South Shetland Islands are significantly more heterogeneous than in the Antarctic Peninsula. 2023-07-24T10:06:19Z 2023-07-24T10:06:19Z 2023-07-06 journal article Parera-Portell, J. A., Mancilla, F. D. L., Almendros, J., Morales, J., & Stich, D. (2023). Slab tearing underneath the Bransfield Strait, Antarctica. Geophysical Research Letters, 50, e2023GL103813. [https://doi.org/10.1029/2023GL103813] https://hdl.handle.net/10481/83951 10.1029/2023GL103813 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional Wiley