Massive earthquake swarm driven by magmatic intrusion at the Bransfield Strait, Antarctica

• Published in: Communications Earth & Environment
• Main Authors: Cesca, Simone, Sugan, Monica, Rudzinski, Łukasz, Vajedian, Sanaz, Niemz, Peter, Plank, Simon, Petersen, Gesa, Deng, Zhiguo, Rivalta, Eleonora, Vuan, Alessandro, Plasencia Linares, Milton Percy, Heimann, Sebastian, Dahm, Torsten
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2022
• Subjects: earthquake swarm magmatic intrusion volcano deformation; Bransfield Strait; King George Island; Antarc*; Antarctica; Orca
• Online Access: http://hdl.handle.net/11585/883907; https://doi.org/10.1038/s43247-022-00418-5; https://www.nature.com/articles/s43247-022-00418-5

An earthquake swarm affected the Bransfield Strait, Antarctica, a unique rift basin in transition from intra-arc rifting to ocean spreading. The swarm, counting ~85,000 volcano-tectonic earthquakes since August 2020, is located close to the Orca submarine volcano, previously considered inactive. Simultaneously, geodetic data reported up to ~11 cm north-westward displacement over King George Island. We use a broad variety of geophysical data and methods to reveal the complex migration of seismicity, accompanying the intrusion of 0.26–0.56 km3 of magma. Strike-slip earthquakes mark the intrusion at depth, while shallower normal faulting the ~20 km long lateral growth of a dike. Seismicity abruptly decreased after a Mw 6.0 earthquake, suggesting the magmatic dike lost pressure with the slipping of a large fault. A seafloor eruption is likely, but not confirmed by sea surface temperature anomalies. The unrest documents episodic magmatic intrusion in the Bransfield Strait, providing unique insights into active continental rifting.