Co-seismic deformation and post-glacial slip rate along the Magallanes-Fagnano fault, Tierra Del Fuego, Argentina

Abstract

Across the extreme south of Patagonia, the Magallanes-Fagnano Fault (MFF) accommodates the left-lateral relative motion between South America and Scotia plates. In this paper, we present an updated view of the geometry of the eastern portion of the MFF outcropping in Tierra del Fuego. We subdivide the MFF in eight segments on the basis of their deformation styles, using field mapping and interpretation of high-resolution imagery. We quantify coseismic ruptures of the strongest recorded 1949, Mw7.5 earthquake, and determine its eastern termination. We recognize several co-seismic offsets in man-made features showing a sinistral shift up to 6.5 m, greater than previously estimated. Using 10Be cosmogenic nuclides depth profiles, we date a cumulated offset in post-glacial morphologies and estimate the long-term slip rate of the eastern MFF. We quantify a 6.4 ± 0.9 mm/a left-lateral fault slip rate, which overlaps geodetic velocity and suggests stable fault behaviour since Pleistocene.