The Motagua Fault is a left-lateral strike-slip fault crossing central Guatemala, tracing the boundary between the North American Plate to the north and the Caribbean Plate to the south. It runs roughly along the valley of the Motagua River and forms the on-land continuation of the Cayman Trough transform system that extends eastward beneath the Caribbean Sea.
As the Caribbean Plate slides eastward relative to North America, the two blocks grind sideways along the Motagua and its parallel companion, the Chixoy-Polochic Fault. This makes central Guatemala a broad zone of transform deformation rather than a single clean fracture.
The fault produced the devastating 1976 Guatemala earthquake, a magnitude 7.5 event that ruptured about 230 kilometres of surface, killed roughly 23,000 people and left more than a million homeless. The disaster remains one of the deadliest earthquakes in the history of the Americas and a defining event in Guatemalan seismic awareness.