Chixoy-Polochic Fault
The Chixoy-Polochic Fault, also known as Cuilco-Chixoy-Polochic Fault, is a major fault zone in Guatemala and southeast Mexico. It runs in a light arc from the east coast of Guatemala to Chiapas, following the deep valleys of the Polochic River, Chixoy River and Cuilco River.
Extent, slip rate and total displacement
The Chixoy-Polochic Fault is a large, dominantly strike-slip, left-lateral fault that runs largely parallel to the Motagua Fault situated some 45 km to its south. Both fault zones are onshore extensions of the Bartlett Deep, or Cayman Trench of the Caribbean Sea, which marks the tectonic boundary between the Caribbean plate and the North American plate. Both faults connect at sea west of the Guatemalan coast. To the west, the Polochic fault may branch onto the Tonala fault of western Chiapas. It does not continue at sea across the Pacific coastal plain and marine shelf.The Chixoy-Polochic fault has total displacement of 125 km, well constrained by the offset of Paleocene or Eocene laramide folds and thrusts. Fault velocity has been estimated at 4.8 ± 2.3 mm/y over the past 10 ky, 2.5–3.3 mm/y over the last 7–10 Myr, and less than 5 mm/y during the current interseismic cycle.