M 7.4 - east of the South Sandwich Islands

Tectonic Summary

The January 2, 2006, M 7.4 South Sandwich Islands earthquake occurred as the result of shallow transform faulting in the South Atlantic Ocean. Focal mechanism solutions indicate that rupture occurred on either an east-west, left-lateral or a north-south, right-lateral strike-slip fault at shallow oceanic lithosphere depths (13 km). At the location of the earthquake, the South America plate translates eastward (left-lateral motion) with respect to the Antartica plate at a velocity of about 14 mm/yr. The earthquake occurred about 300 km east of a complex plate triple junction between the South America, Antarctica, and Scotia plates and close to the America-Antarctic Ridge that represents the South America:Antarctica boundary. Given the strike-slip nature and location of the event, the earthquake likely resulted from left-lateral (east-west oriented) relative motion between the South America and Antarctica plates.

Several large earthquakes have occurred along this portion of the plate boundary, including events of M 7.2 in October 1983, close to the aforementioned triple junction, and M 7.0 in October 1973, 20 km north of the January 2, 2006, earthquake. Due to the remoteness of this location, none of these events are known to have caused any associated fatalities or damage.

Hayes et al. (2016) Tectonic summaries of magnitude 7 and greater earthquakes from 2000 to 2015, USGS Open-File Report 2016-1192. (5.2 MB PDF)