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

Abstract

Tierra del Fuego is an island in southernmost South America shared by Chile and Argentina. Three major cities add to a permanent population of 300,000, rapidly growing through immigration, and a touristic influx in the order of 200,000 annually. Tierra del Fuego is a seismic region. Instrumental records exist of four earthquakes of magnitude between 7.0 (two events) and 7.8 (two events) since 1949, and low intensity events are felt by the population every couple of years. The Magallanes-Fagnano (MF) transform fault, which crosses the island with an east-west trend, is recognized as a seismogenic source. Widely published calculations for the two M = 7.8 seismic events appear to indicate, however, that there might be another source in northern Tierra del Fuego island. This paper argues that the MF fault is the only significant source of earthquakes in this region, accounting for all the high-magnitude (instrumental and preinstrumental) seismic events. In addition it presents evidence for coseismic deformation in strandplains located at more than 300 km from the trace of the MF fault, in support for high-magnitude seismicity affecting Tierra del Fuego throughout the Holocene.