Back-Arc Extension of the Central Bransfield Basin Induced by Ridge–Trench Collision: Implications From Ambient Noise Tomography and Stress Field Inversion

• Published in: Geophysical Research Letters
• Main Authors: Li, Wei, Almendros González, Francisco Javier
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2021
• Subjects: Ambient noise tomography; S-wave velocity structure; Back-arc extension; Ridge-trench collision; Bransfield Basin; Phoenix Plate; Antarctic; The Antarctic; Antarctic Peninsula; Pacific; Fernandez; Carmona; Hero Fracture Zone; Antarc*
• Online Access: http://hdl.handle.net/10481/72138; https://doi.org/10.1029/2021GL095032

The authors appreciate the efforts of all the BRAVOSEIS team members, including Enrique Carmona, Rafa Abella, Paco Carrion, Feli Agui, Alfonso Ontiveros, Jose Luis Granja, Ivan Fernandez, and Rabea Sondershaus, in collecting the data used in this study. The authors thank the German Instrument Pool for Amphibian Seismology (DEPAS, Schmidt-Aursch & Haberland, 2017) for providing seismic instruments for networks 5M and ZX. The authors thank all participants in the BRAVOSEIS 2018, 2019, and 2020 cruises and all staff involved in the realization of the surveys. We use the Generic Mapping Tools (Wessel et al., 2013) to generate the figures. This research is jointly supported by the BRAVOSEIS project (CTM2016-77315-R), AWI, and GFZ. W. Li is also supported by the National Natural Science Foundation of China (41804056) and the Sino-German (CSC-DAAD) Postdoc Scholarship. Constructive comments from the associate editor and two anonymous reviewers helped improve the manuscript. Open access funding enabled and organized by Projekt DEAL. The Bransfield Basin is a young (∼4 Ma) back-arc basin related to the remnant subduction of the Phoenix Plate that once existed along the entire Pacific margin of the Antarctic Peninsula. Based on a recently deployed amphibious seismic network, we use ambient noise tomography to obtain the S-wave velocity structure in the Central Bransfield Basin (CBB). Combining with the stress field inverted from focal mechanisms, our images reveal that the CBB suffers a significant extension in the northwest-southeast direction. The extension is strongest in the northeastern CBB with associated mantle exhumation and weakens to the southwest with decoupled deformations between the upper crust and lithospheric mantle. Such an along-strike variation of extension can be explained by slab window formation and forearc rotation, which are associated with the Phoenix Plate detachment during the ridge– trench collisions at the southwest of the Hero Fracture Zone. BRAVOSEIS project CTM2016-77315-R AWI GFZ National Natural Science Foundation of China (NSFC) 41804056 Sino-German (CSC-DAAD) Postdoc Scholarship Projekt DEAL