M 7.2 - 9 km ENE of Coyuquilla Norte, Mexico

Tectonic Summary

The April 18, 2014, M 7.2 earthquake near the Pacific Coast of Mexico occurred as the result of shallow reverse faulting in the state of Guerrero, 265 km southwest of Mexico City. The initial location, depth, and mechanism of the April 18th earthquake are broadly consistent with slip on or near the plate boundary interface between the subducting Cocos oceanic plate and the North America plate. The broad-scale tectonics of the Pacific Coast of Mexico are controlled by the northeastward subduction of the Cocos plate beneath the North America plate at a rate of approximately 65 mm/yr. 

Earthquakes are a common occurrence along the Middle America subduction zone. The April 18th earthquake occurred northwest of the rupture area of the 1957 M 7.8 Guerrero earthquake, and since 1975, 23 events of M 6+ have occurred within 200 km of the April 18th earthquake, including events of M 8.0 and M 7.6 (September 1985), M 7.2 (October 1981), and M 7.5 (March 1979), all to the northwest of the April 18th epicenter. The 1981 and 1979 events caused nine and five shaking-related fatalities, respectively. The 1985 M 8.0 earthquake, 195 km to the northwest of the April 2014 event, led to more than 9,500 fatalities, mostly in Mexico City, and generated small, local tsunamis. That event was influential in initiating efforts to establish earthquake early warning systems in Mexico City.

The April 18th earthquake occurred within the “Guerrero Seismic Gap”—an approximately 200-km-long segment of the Cocos-North America plate boundary identified to have experienced no significant earthquakes since 1911 when a M 7.6 event occurred. The plate interface in this region is known to be locked, and an earthquake of M 8.1–8.4 is thought possible if the entire gap ruptures in a single event.

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)