M 7.0 - southern East Pacific Rise

Tectonic Summary

The October 9, 2014, M 7.0 earthquake near the Southern East Pacific Rise occurred as the result of shallow, oblique reverse faulting in the complex plate boundary region at the intersection of the Pacific, Nazca and Antarctic plates, nearly 600 km to the south of Easter Island. Focal mechanism solutions indicate that oblique rupture occurred on a moderately dipping reverse fault striking to the west-northwest or to the east. Of these two possible fault orientations, finite-fault modeling of globally recorded seismic data is more consistent with slip on the east-striking reverse fault. At the location of the earthquake, about 100 km to the east of the East Pacific Rise, the Nazca plate diverges from the Pacific at a velocity of about 150 mm/yr in a direction slightly south of due east. Some authors identify a small microplate, called the Juan Fernandez plate, in this region; the October 9th earthquake occurred near the northern boundary of this tectonic block with the broader Nazca plate.

Moderate-sized earthquakes are common in this region of the East Pacific Rise, though events of this size have been rare over the past century.  Fifteen other M 6+ earthquakes have occurred within 500 km of the 2014 event over the preceding century—until October 9, 2014, none had been larger than a M 7.0 earthquake that occurred in March 1920, 400 km due south of the October 9, 2014, earthquake. Because of the remote location far from population centers that might be vulnerable to earthquake shaking, none of these events are known to have caused damage. The M 7.1 2014 event was followed by a M 6.6 aftershock 18 minutes later.

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)