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Bending the Bolivian orocline in real time

¹ Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, New York 14853-1504, USA
² Center for Earthquake Research and Information, University of Memphis, 3890 Central Avenue, Suite 1, Memphis, Tennessee 38152, USA
³ Geodetic Science, The Ohio State University, 470 Hitchcock Hall, 2070 Neil Avenue, Columbus, Ohio 43210, USA
⁴ Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, New York 14853-1504, USA
⁵ School of Ocean and Earth Science and Technology, University of Hawaii, 1680 East-West Road, Honolulu, Hawaii 96822, USA

Global positioning system (GPS) data from the central Andes record vertical axis rotations that are consistently counterclockwise in Peru and Bolivia north of the bend in the mountain belt, and clockwise to the south in southern Bolivia, Argentina, and Chile. These geologically instantaneous rotations have the same sense as rotations that have accrued over millions of years and are recorded by paleomagnetic and geologic indicators. The change in sign of the rotation at both decadal and million-year time scales occurs across the axis of topographic symmetry that defines the Bolivian orocline. When extrapolated to a common time interval, the magnitudes of rotation from geologic features and from GPS are surprisingly similar, given that a significant part of the instantaneous deformation field is probably elastic and due to interseismic locking of the plate boundary. Some of the interseismic deformation field must reflect permanent deformation, and/or some of the current elastic deformation will be converted to upper-plate permanent deformation over time rather than be recovered by elastic rebound during interplate earthquakes. We suggest that the spatial patterns of the elastic and the permanent modes of bending are similar because they are driven by the same stress field.

Key Words: central Andes • orocline • rotation • global positioning system • paleomagnetism

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