Seismo en Tierra del Fuego
Descripción de la ubicación de Movimientos Actuales

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Seismo actual en América del Sur y zona de influencia

(Fuente: USGS y UTIG)

The neotectonic evolution of the Antarctic Peninsula and Scotia Sea is extremely complex. Understanding the recent evolution of the Drake-Scotia-Antarcticia-South America plate intersections will provide important information as to how major plate boundaries reorganize after demise of a long-lived spreading center and the consequential reduction in the number of plates. The plate reorganization probably resulted in the uplift of the Shackleton Ridge which may have effected the sedimentary patterns in both the Scotia Sea and possibly the Weddell Sea. If the break of the Shackleton transform fault can be traced with multibeam and sidescan sonar as it intersects the southern end of South America then the orientation and geometry of the faults, fractures and deformation as the transform fault intersects the South American continent will help to interpret the structures in that complex region.

ANTARCTICA IS THE EARTH'S most isolated continent. It is surrounded by actively spreading ridges except in the South American sector. The motion of South America with respect to Antarctica is latitudinal and left-lateral at approximately 22 mm per year and is distributed along the boundaries of the intervening Scotia plate.

A prominent but discontinuous bathymetric high known as the Scotia Ridge surrounds the Scotia plate on three sides. This feature includes some continental material detached from the South American and Antarctic continents, but its eastern closure is a volcanically and seismically active group of islands, the South Sandwich arc, that is separated from the Scotia plate by a vigorously spreading back- arc ridge. The entire east-closing, locally emergent bathymetric feature joining the two continents, is known as the Scotia arc. The D- shaped Sandwich plate and arc appear to be moving rapidly east with respect to both South America and Antarctica, thereby for the first time introducing a subduction system into the otherwise rift-bounded South Atlantic Ocean basin. This motion may constitute the best evidence for mantle return flow from the closing Pacific Ocean basin to the expanding Atlantic Ocean basin. The Scotia arc is nonetheless one of the most poorly constrained of the major tectonic systems on Earth, yet it is a critical...
"Collaborative Research: Scotia Arc GPS Project (SCARP)"

The new multichannel seismic (MCS) data reveal a complex array of rifting styles short of clearly-defined sea floor spreading. The Strait is undergoing basinwide extension. While E-MORB basalts have been dredged from en echelon topographic highs in the NE part of the basin, available seismic evidence does not support the formation of oceanic crust there. Volcanic crust acoustic signatures at known axial deep highs also extend laterally sub-sea floor; their distribution and style of intrusion support propagation of volcanism and associated extension from NE-to-SW. Active extensional structures along both margins control a strong physiographic asymmetry. The South Shetland Islands margin is comprised of a few, closely-spaced, large-offset normal faults; the gentler Antarctic Peninsula margin exhibits broader, distributed extension. To the NE, normal fault polarity reversals (NFPRs) dominate; listric faults sole into NW-dipping, low-angle reflectors interpreted as detachments. To the SW, larger NFPRs and convex-up geometries up to ~20 km across suggest broad uplift rather than detachment-based extension. Structural relief is also subdued in the SW. We suggest that such uplift precedes sea floor volcanism and rapid associated deflation along detachments. This coupled uplift/deflation, and the observed overall NE-to-SW propagation of rifting, leads to ~NW-SE trending accommodation zones segmenting the basin along-strike. Locations of these accommodation zones may be determined by structural grains in the preexisting crust.
Observed extension in Bransfield Strait may result both from plate boundary tectonics at the South Shetland Trench and at the evolving Antarctic-Scotia plate boundary. Extension was probably initiated by onset of subduction rollback at the trench, as a slab window opened from the SW. Rollback of older, subducting lithosphere at the trench's NE end is therefore more rapid, thus driving SW-propagating extension. Left-lateral transtension as a result of reorganization of the triple junction at the intersection of the Shackleton Fracture Zone and South Scotia Ridge may also augment extension in NE Bransfield Strait (from the Abstract - Barker and Austin, Journal of Geophysical Research, in press).