The Chixoy-Polochic Fault, also known as Cuilco-Chixoy-Polochic Fault, is a major fault zone in

Guatemala Guatemala, officially the Republic of Guatemala, is a country in Central America. It is bordered to the north and west by Mexico, to the northeast by Belize, to the east by Honduras, and to the southeast by El Salvador. It is hydrologically b ...

and southeast

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

. It runs in a light arc from the east coast of Guatemala to

Chiapas Chiapas, officially the Free and Sovereign State of Chiapas, is one of the states that make up the Political divisions of Mexico, 32 federal entities of Mexico. It comprises Municipalities of Chiapas, 124 municipalities and its capital and large ...

, following the deep valleys of the Polochic River,

Chixoy River The Chixoy River or Río Chixoy is a river in Guatemala. The river is called Río Negro from its sources in the highlands of Huehuetenango and El Quiché until it reaches the Chixoy hydroelectric dam (located at ), where the Río Salamá and Rio ...

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 The Motagua Fault (also, Motagua Fault Zone) is a major, active fault, active left lateral-moving transform fault which cuts across Guatemala. It forms part of the tectonic boundary between the North American plate and the Caribbean plate. It i ...

situated some 45 km to its south. Both fault zones are onshore extensions of the Bartlett Deep, or Cayman Trench of the

Caribbean Sea The Caribbean Sea is a sea of the Atlantic Ocean, North Atlantic Ocean in the tropics of the Western Hemisphere, located south of the Gulf of Mexico and southwest of the Sargasso Sea. It is bounded by the Greater Antilles to the north from Cuba ...

, 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.

Seismicity

While recent seismic activity is more prominent in the Motagua fault, some studies suggest the Chixoy-Polochic Fault is still capable of producing major earthquakes. The magnitude 7.5–7.8 M_w

1816 Guatemala earthquake The 1816 Guatemala earthquake occurred at 15:30 Coordinated Universal Time, UTC on 22 July. It had an estimated magnitude of 7.5 to 7.75 on the and a maximum perceived intensity of IX ''(Violent)'' on the Mercalli intensity scale. The quake, at a ...

of western Guatemala has been ascribed to the Polochic Fault, although this has been disputed. Most recent recorded fault activity includes at least for slip events between 17 ka and 13 ka BP, and aseismic

surface rupture In seismology, surface rupture (or ground rupture, or ground displacement) is the visible offset of the ground surface when an earthquake rupture along a Fault (geology), fault affects the Earth's surface. Surface rupture is opposed by buried rup ...

over some of the past 5 centuries. One or several intermediate to large earthquakes between 850 CE and 1,400 CE, including a cluster of 4 earthquakes over 60 years during the

Classic Maya collapse In archaeology, the classic Maya collapse was the destabilization of Classic Maya civilization and the violent collapse and abandonment of many southern lowlands city-states between the 7th and 9th centuries CE. Not all Mayan city-states ...

. The fault display a 5 km to 10 km deep zone of microseismicity which may represent a locked zone. Only ≤ 5.6 M_w earthquakes have occurred on the fault since the beginning of regional instrumental records (1920 CE).

References

{{Faults Chixoy Geographic areas of seismological interest Geology of Guatemala Seismic faults of Guatemala