Seismotectonic implications of the South Chile ridge subduction beneath the Patagonian Andes. (24th February 2021)

• Record Type: Journal Article
• Authors: Suárez, Rodrigo; Sue, Christian; Ghiglione, Matías; Guillaume, Benjamin; Ramos, Miguel; Martinod, Joseph; Barberón, Vanesa
• Is Part Of: Terra nova. Volume 33:Number 4(2021)
• Page Start: 364
• Page End: 374
• Publication Date: 2021-02-24
• Subjects: earthquake focal mechanism -- intraplate seismic gap -- Patagonia slab window -- South Chile ridge; Earth sciences -- Periodicals; Geology -- Periodicals; 550
• DOI: 10.1111/ter.12521
• Languages: English
• ISSNs: 0954-4879

Abstract

Abstract: The South Chile ridge (SCR) intersects the Patagonian trench around 46°09′S, forming the triple junction among the Antarctic, Nazca, and South America plates. Subduction of the SCR since ~18 Ma produced the opening of a slab window beneath Patagonia and a noticeable magmatic gap in the cordillera, profuse volcanism and topographic uplift in the retroarc. To study seismicity distribution and present‐day stress resulting from this particular framework, we analyse databases of seismic events and earthquake focal mechanisms. Our study finds that clusters of intraplate crustal seismic events are disrupted by a ~450–470 km seismicity gap above the slab window. Calculated stress tensors depict a strike‐slip tectonic regime north of the triple junction, and ~W‐E compression to the south of the seismic gap. We propose that the seismotectonic behaviour of the upper plate is disturbed at the first order by the trench‐ridge intersection, leading to a heterogeneous stress field.