M 7.3 - 74 km S of Intipucá, El Salvador

Tectonic Summary

The October 14, 2014, M 7.3 earthquake off the coast of El Salvador occurred as the result of shallow normal faulting in the Central America subduction zone. Focal mechanism solutions indicate that rupture occurred on either a steeply northeast-dipping fault or on a fault dipping shallowly to the southwest. The location, depth (40 km), and faulting mechanism of the earthquake are consistent with its occurrence either within the subducting oceanic Cocos plate, or in the accretionary wedge of the overriding Caribbean plate, rather than on the main subduction zone thrust. Finite-fault modeling of globally recorded seismic data for this earthquake is not able to distinguish between these two possibilities. At the location of this event, the Cocos plate is converging with the Caribbean plate at a rate of about 73 mm/yr in an east-northeast direction. The approximate depth of the subducted Cocos plate at the location of the earthquake is 50 km.

The portion of the Middle America subduction zone bordering El Salvador and Nicaragua, locus of the October 14th earthquake, is very seismically active, with events of M 7.3 (2012), M 7.7 (2001), M 7.7 (1992), and M 7.3 (1982) all having occurred within 200 km of the October 14th earthquake in the past 35 years. The 2001 M 7.7 earthquake involved normal faulting with similar orientation to the October 14th event, and likely occurred within the subducting Cocos plate. It caused substantial damage in El Salvador and Guatemala, with the majority of fatalities caused by a triggered landslide. The 2001 earthquake also triggered aftershocks in the overriding Caribbean plate, including a M 6.6 event in the vicinity of San Salvador.

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)