FN Archimer Export Format PT J TI Microseismicity and lithosphere thickness at a nearly-amagmatic oceanic detachment fault system BT AF Chen, Jie Crawford, Wayne C. Cannat, Mathilde AS 1:1;2:1;3:1; FF 1:;2:;3:; C1 Université Paris Cité, Institut de physique du globe de Paris, CNRS, F-75005, Paris, France C2 UNIV PARIS CITE, FRANCE IN DOAJ IF 16.6 TC 7 UR https://archimer.ifremer.fr/doc/00819/93062/99505.pdf https://archimer.ifremer.fr/doc/00819/93062/99506.pdf https://archimer.ifremer.fr/doc/00819/93062/99507.pdf https://archimer.ifremer.fr/doc/00819/93062/99508.zip LA English DT Article CR MD 199 / SISMO-SMOOTH ROVSMOOTH BO Marion Dufresne Pourquoi pas ? AB Oceanic detachment faults play a central role in accommodating the plate divergence at slow-ultraslow spreading mid-ocean ridges. Successive flip-flop detachment faults in a nearly-amagmatic region of the ultraslow spreading Southwest Indian Ridge (SWIR) at 64°30’E accommodate ~100% of plate divergence, with mostly ultramafic smooth seafloor. Here we present microseismicity data, recorded by ocean bottom seismometers, showing that the axial brittle lithosphere is on the order of 15 km thick under the nearly-amagmatic smooth seafloor, which is no thicker than under nearby volcanic seafloor or at more magmatic SWIR detachment systems. Our data reveal that microearthquakes with normal focal mechanisms are colocated with seismically-imaged damage zones of the active detachment fault and of antithetic hanging-wall faults. The level of the hanging-wall seismicity is significantly higher than that documented at more magmatic detachments of slow-ultraslow ridges, which may be a unique feature of nearly-amagmatic flip-flop detachment systems. PY 2023 PD JAN SO Nature Communications SN 2041-1723 PU Springer Science and Business Media LLC VL 14 IS 1 UT 001008541400013 DI 10.1038/s41467-023-36169-w ID 93062 ER EF