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.
It does not continue at sea across the Pacific coastal plain and marine shelf.
[2] The Chixoy-Polochic fault has total displacement of 125 km, well constrained by the offset of Paleocene or Eocene laramide folds and thrusts.
[3] Fault velocity has been estimated at 4.8 ± 2.3 mm/y over the past 10 ky,[4] 2.5–3.3 mm/y over the last 7–10 Myr,[5] and less than 5 mm/y during the current interseismic cycle.
Only ≤ 5.6 Mw earthquakes have occurred on the fault since the beginning of regional instrumental records (1920 CE).