M 7.0 - southern Mid-Atlantic Ridge

Tectonic Summary

The June 17, 2015, M 7.0 southern Mid-Atlantic Ridge earthquake occurred as the result of left-lateral strike-slip faulting on or near a transform fault forming part of the South America:Africa (Nubia) plate boundary.  At the location of this earthquake, the South America plate moves approximately westward at a rate of 33 mm/yr with respect to the Nubia plate. While historical earthquakes have occurred in the same region and likely on the same fault as this earthquake, the fracture zone does not appear to be named.

Moderate to large earthquakes in this region of the south Atlantic are common—over the past century, 16 other earthquakes of M 6.0–6.6 have occurred within 250 km of the June 17, 2015, event, both along the same fracture zone and in association with other shorter fracture zones to the south. The June 17, 2015, event represents the largest in the region over that time period; the next largest was a M 6.6 event in February 2005, 130 km to the south. None of these earthquakes are known to have caused damage.  Their remoteness from populated land minimizes the potential hazard from shaking damage, and their strike-slip faulting mechanisms produce relatively small vertical tectonic displacement of the sea-floor, which minimizes the risk of their producing destructive tsunami.

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)