M 7.0 - 43 km SSW of Masachapa, Nicaragua

Tectonic Summary

The October 9, 2004, M 7.0 earthquake near the coast of Nicaragua occurred as the result of shallow thrust faulting just east of the Middle America Trench at the interface between the Cocos and Caribbean plates. The northwest-southeast-trending trench marks the boundary where the Cocos plate begins subducting beneath the overriding Caribbean plate at a rate of about 80 mm/yr.

In addition to interface thrust fault earthquakes, shallow strike-slip earthquakes occur within the deforming crust of the overriding Caribbean plate as well as within the subducting Cocos plate from shallow depths to depths of more than 200 km. The world’s largest earthquakes have been interface thrust fault earthquakes, including the 1960 M 9.5 Chilean earthquake and the 1964 M 9.2 Alaskan earthquake. Historically, however, the most damaging Nicaraguan earthquakes have been earthquakes occurring beneath population centers at shallow depths in the Caribbean plate. The 1972 M 6.2 Managua earthquake, for example, destroyed the center of the city and resulted in an estimated 6,000 fatalities.

This region of Central America hosts large earthquakes fairly regularly. Within 400 km of the October 9th event, there were five other earthquakes of M 7+ over the preceding 40 years. One of the largest and closest of these events was a M 7.7 earthquake in September 1992 roughly 50 km to the northwest that resulted in hundreds of fatalities and widespread damage, mostly associated with a tsunami generated by that 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)