Geodetic determination of relative plate motion and crustal deformation across the Scotia‐South America plate boundary in eastern Tierra del Fuego

Abstract

Global Positioning System (GPS) measurements provide the first direct measurement of plate motion and crustal deformation across the Scotia‐South America transform plate boundary in Tierra del Fuego. This plate boundary accommodates a part of the overall motion between South America and Antarctica. The subaerial section of the plate boundary in Tierra del Fuego, about 160 km in length, is modeled as a two dimensional, strike‐slip plate boundary with east‐west strike. Along the Magallanes‐Fagnano fault system, the principal fault of this portion of the plate boundary, relative plate motion is left‐lateral strike‐slip on a vertical fault at 6.6 ± 1.3 mm/year based on an assumed locking depth of 15 km. The site velocities on the Scotia Plate side are faster than the relative velocity by an additional 1–2 mm/yr, suggesting there may be a wider region of diffuse left‐lateral deformation in southern Patagonia. The north‐south components of the velocities, however, do not support the existence of active, large‐scale transpression or transtension between the South America and Scotia plates along this section of the plate boundary.