M 7.1 - north of Ascension Island

  • 2016-08-29 04:29:57 (UTC)
  • 0.046°S 17.826°W
  • 10.0 km depth

Tectonic Summary

The August 29, 2016 M 7.1 earthquake north of Ascension Island, in the south Atlantic Ocean, occurred as the result of strike-slip faulting on or near the Mid-Atlantic Ridge plate boundary separating the Nubia (Africa) and South America plates. The preliminary location and focal mechanism solution of the earthquake are consistent with the event being associated with right lateral strike-slip faulting on the Romanche Transform (the seismically active section of the Romanche Fracture Zone), though more detailed analyses of the event will be required to definitively determine the causative fault. At the location of this earthquake, the Nubia and South America plates diverge at a rate of approximately 29 mm/yr, in an east-west direction.

Moderate-to-large earthquakes on the Romanche Transform are common – over the past century, six other earthquakes of M 6.5-6.8 have occurred within 250 km of the August 29, 2016 event, likely along the same fault. The largest of these was a M 6.8 event on August 28, 1973, 43 years and 1 day before today’s M 7.1 earthquake and approximately 30 km to the southwest. Because of their strike-slip mechanisms and locations in the remote south Atlantic (about 950 km north-northwest of Ascension Island), none of these historic events are known to have generated tsunami or caused damage.

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