Mantle flow through a tear in the Nazca slab inferred from shear wave splitting

• Published in: Geophysical Research Letters
• Main Authors: Lynner, Colton, Anderson, Megan L., Portner, Daniel Evan, Beck, Susan, Gilbert, Hersh
• Other Authors: Univ Arizona, Dept Geosci, Department of Geosciences; University of Arizona; Tucson Arizona USA, Department of Geology; Colorado College; Colorado Springs Colorado USA, Department of Geoscience; University of Calgary; Calgary Alberta Canada
• Format: Article in Journal/Newspaper
• Language: English
• Published: AMER GEOPHYSICAL UNION 2017
• Subjects: shear wave splitting; flat slab; slab tear; mantle dynamics; Argentina; Seismological Facilities for the Advancement of Geoscience and EarthScope
• Online Access: http://hdl.handle.net/10150/625357; https://doi.org/10.1002/2017GL074312

A tear in the subducting Nazca slab is located between the end of the Pampean flat slab and normally subducting oceanic lithosphere. Tomographic studies suggest mantle material flows through this opening. The best way to probe this hypothesis is through observations of seismic anisotropy, such as shear wave splitting. We examine patterns of shear wave splitting using data from two seismic deployments in Argentina that lay updip of the slab tear. We observe a simple pattern of plate-motion-parallel fast splitting directions, indicative of plate-motion-parallel mantle flow, beneath the majority of the stations. Our observed splitting contrasts previous observations to the north and south of the flat slab region. Since plate-motion-parallel splitting occurs only coincidentally with the slab tear, we propose mantle material flows through the opening resulting in Nazca plate-motion-parallel flow in both the subslab mantle and mantle wedge. NSF [EAR-0738935, EAR-0739001, EAR-1565475]; Colorado College Patricia Buster Scholarship Fund; National Science Foundation through the Seismological Facilities for the Advancement of Geoscience and EarthScope (SAGE) Proposal of the National Science Foundation [EAR-1261681] 6 month embargo; published online: 13 July 2017 This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [e-mail].