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- Title
Slab Tearing Underneath the Bransfield Strait, Antarctica.
- Authors
Parera‐Portell, J. A.; Mancilla, F. D. L.; Almendros, J.; Morales, J.; Stich, D.
- Abstract
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. Plain Language Summary: With more seismic stations than ever before, we investigate the structure of the earth beneath the Bransfield Strait (West Antarctica), a region located behind a subduction zone which features active volcanism and extension of the crust. We imaged for the first time in the region a gap in the sinking Phoenix plate which coincides with the position of the 2020–2021 Orca earthquake series. We located the two major earthquakes at the base of the crust, so we link seismicity to the flow of hot materials through the gap in the Phoenix plate and its accumulation at the base of the crust. We imaged this layer below Deception Island, and also identified a widespread area where melting probably occurs. The average thickness and seismic velocities of the crust resemble standard values of areas undergoing extension, although the South Shetland Islands are highly heterogeneous. Key Points: Slab tearing occurs along an ancient fracture zone in the subducted Phoenix plateActive magmatic underplating could trigger the Orca earthquake swarm
- Subjects
ANTARCTICA; SHETLAND (Scotland); PHOENIX (Ariz.); BACK-arc basins; SLABS (Structural geology); EARTHQUAKE swarms; STRAITS; SEISMIC wave velocity; SUBDUCTION zones; SUBDUCTION; VOLCANISM
- Publication
Geophysical Research Letters, 2023, Vol 50, Issue 13, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2023GL103813