000005802 001__ 5802 000005802 005__ 20220620170019.0 000005802 037__ $$aCTALK-2022-0067 000005802 100__ $$aAmmirati, Jean-Baptiste 000005802 245__ $$aWhat can we learn from the 2021 (Mw 6.4) San Juan earthquake in terms of crustal deformation above the Chile-Argentina flat slab? 000005802 260__ $$c2021 000005802 269__ $$c2021-12-14 000005802 520__ $$aUnderstanding the mechanisms of crustal deformation along convergent margins is critical to identifying potential seismogenic structures and evaluating earthquake hazards for nearby urban centers. In the southern central Andes (28–33ºS), along-strike variations in subduction dip angle have been linked to high upper-crustal shortening and characterized by an elevated retroarc seismicity. Over the years, several large magnitude earthquakes were responsible for many casualties and caused infrastructural damage to cities in western Argentina. Although several studies largely contributed to better understand the nature and evolution of the Argentine retroarc, some key aspects remain poorly understood: 1) The discrepancy between subduction-parallel ENE-WSW regional stress evidenced by 30 years of seismic and geodetics monitoring and the EW trench-normal compressional deformation markers characterizing the retroarc. 2) The presence of an abnormally thick crust (~60 km) with deep crustal seismicity within its basement (20-40 km). The January 19th 2021 (Mw6.4) San Juan earthquake can be analyzed in the framework of historical and modern seismicity to investigate and clarify the mechanisms controlling the tectonic evolution of the Argentine retroarc. The deep crustal character (23-24 km depth) of this earthquake and its strike-slip, right-lateral focal mechanism strengthens the idea of deformation partitioning along basement faults and upper-crust structures in response to the oblique convergence of the Nazca and South American plates. Seismogenic basement faults such as the mid-crustal structure activated during the 2021 San Juan earthquake have significant implications for seismic risk in western Argentina, and may transfer shortening to active upper-crustal faults associated with historically devastating shallow earthquakes. 000005802 594__ $$aNO 000005802 700__ $$aMackaman-Lofland, Chelsea 000005802 700__ $$aZeckra, Martin 000005802 773__ $$tAGU Fall Meeting 2021, New Orleans, USA 000005802 8560_ $$fmartin.zeckra@observatory.be 000005802 85642 $$ahttps://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/883543 000005802 906__ $$aContributed 000005802 980__ $$aCTALKCONT