Motagua Fault

The Motagua fault is a transform fault in Guatemala and southeastern Mexico. It is located in the south of the Mexican state of Chiapas, and follows the linear course of the Motagua River from the coast of the Caribbean Sea to Chichicastenango in the El Quiché department, crossing through Guatemala and Belize. It is part of the Motagua-Polochic fault system, and has a left lateral strike movement, being part of the fault system that forms the boundary between the North American plate and the Caribbean plate. This fault divides two very different terrains: the Maya Block to the north and the Chortis block to the south.

This fault represents the tectonic separation of the North American plate and the Caribbean plate, like the Chixoy-Polochic Fault, when it enters the Caribbean Sea it passes very close to Cuba, Haiti, and the Dominican Republic then joins in the Antilles Menores and turns south to join together and make the tectonic division of the South American plate and the Nazca plate, then it turns north and makes a division of the Cocos plate to follow the same route again. This fault gives seismic influences on Chiapas, Guatemala, Belize and the Lesser Antilles, apart from causing volcanic phenomena, which give rise to the volcanoes of Guatemala, Chiapas and those of the Lesser Antilles.

History

This fault formed along a suture zone 70 to 65 million years ago. Before this suture (from 120 million years ago, in the middle Cretaceous) it is thought to have constituted a subduction boundary.

Kinematics

The total strike-slip displacement along the Chixoy-Polochic fault is close to 130 km (Burkart, 1978), and has occurred in the last 10.3 million years. Based on these values, this fault has a displacement rate (average over long period) of 13 mm per year.

Little is known about the displacement of the Motagua fault, however, the displacement of recent sedimentary deposits suggests a displacement between 6 and 10 mm per year.

Earthquakes

Several earthquakes have been produced on this fault, one of the best known being the Guatemala earthquake of February 4, 1976. This earthquake ruptured 320 km along the Motagua fault. The Chixoy-Polochic fault was ruptured during a strong earthquake in 1816 (White,1985).