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

Abstract

[1] 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 strikeslip 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 northsouth 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.Components: 9235 words, 7 figures, 2 tables.

Tectonic reconstructions for paleobathymetry in Drake Passage

“…1) in the Scotia Sea region have been modelled using both seismic slip vector and GPS data. Used separately or in combination, the two techniques agree on the presence of two independently-moving plates inside the Scotia Arc, the larger Scotia Plate in the west and, further east, the smaller Sandwich Plate, which diverge from one another at the north-striking east Scotia ridge along 30°W (Forsyth, 1975;Pelayo and Wiens, 1989;Smalley et al, 2003Smalley et al, , 2007Thomas et al, 2003). Smalley et al (2007) show that the use of GPS data much reduces the uncertainties in solutions for the directions and rates of motions between these plates and their larger neighbours outside the Scotia Arc.…”

Late Pleistocene and Holocene palaeoenvironmental changes in central Tierra del Fuego (~54°S) inferred from pollen analysis

“…Bedrock exposures are rare, as Quaternary glacial deposits and peat bogs cover most of the landscape. The Magallanes-Fagnano transforming fault system separates both mountain alignments, forming a tectonic valley with a left-lateral slip rate of 5-6 mm y -1 (Smalley et al 2003). Vertical displacements of 0-1 m with no coseismic horizontal strike-slip displacement occurred twice during the last 8,000 years along the bottom of the valley where La Correntina mire is situated (Costa et al 2006).…”

Paleoseismicity and seismic hazard in southern Patagonia (Argentina-Chile; 50°–55°S) and the role of the Magallanes-Fagnano transform fault

“…The principal trace of the MF fault is, in fact, a series of vertical fault segments arranged with an en e´chelon geometry and shows a restraining bend between 68°30'W and 70°W, with a northward concavity ( Fig. 1; Smalley et al 2003;Lodolo et al 2003). Geodetic GPS measurements indicate relative motion across the MF fault system at rates between 0.66 and 0.96 cm/year (Smalley et al 2003;DeMets et al 2010).…”