Poster of the Nicaragua Earthquake of 9 October 2004 - Magnitude 6.9

Tectonic Summary

This thrust-fault earthquake occurred just east of the Middle America Trench at the interface between the Cocos and the 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 millimeters per year. In addition to interface thrust-fault earthquakes, shallow strike-slipearthquakes occur within the deforming crust of the overriding Caribbean plate, and earthquakes occur within the subducting Cocos plate from shallow depths to depths of over 200 km. The world's largest earthquakes have been interface thrust-fault earthquakes, including the 1960 magnitude 9.5 Chilean earthquake and the 1964 magnitude 9.2 Alaskan earthquake. Historically, however, the most damaging Nicaraguan earthquakes have been earthquakes occurring beneath population centers at shallow depth in the Caribbean plate. The 1972 magnitude 6.2 Managua earthquake, for example, destroyed the center of the city and killed an estimated 6000 people.


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