The Chixoy-Polochic Fault, also known as Cuilco-Chixoy-Polochic Fault, is a major fault zone in Guatemala and southwestern 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.
Guatemala, officially the Republic of Guatemala, is a country in Central America bordered by Mexico to the north and west, Belize and the Caribbean to the northeast, Honduras to the east, El Salvador to the southeast and the Pacific Ocean to the south. With an estimated population of around 16.6 million, it is the most populated country in Central America. Guatemala is a representative democracy; its capital and largest city is Nueva Guatemala de la Asunción, also known as Guatemala City.
Mexico, officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatemala, Belize, and the Caribbean Sea; and to the east by the Gulf of Mexico. Covering almost 2,000,000 square kilometres (770,000 sq mi), the nation is the fifth largest country in the Americas by total area and the 13th largest independent state in the world. With an estimated population of over 120 million people, the country is the eleventh most populous state and the most populous Spanish-speaking state in the world, while being the second most populous nation in Latin America after Brazil. Mexico is a federation comprising 31 states and Mexico City, a special federal entity that is also the capital city and its most populous city. Other metropolises in the state include Guadalajara, Monterrey, Puebla, Toluca, Tijuana and León.
Chiapas, officially the Free and Sovereign State of Chiapas, is one of the 31 states that along with the federal district of Mexico City make up the 32 federal entities of Mexico. It is divided into 124 municipalities as of September 2017 and its capital city is Tuxtla Gutiérrez. Other important population centers in Chiapas include Ocosingo, Tapachula, San Cristóbal de las Casas, Comitán and Arriaga. It is the southernmost state in Mexico. It is located in Southeastern Mexico, and it borders the states of Oaxaca to the west, Veracruz to the northwest and Tabasco to the north, and by the Petén, Quiché, Huehuetenango and San Marcos departments of Guatemala to the east and southeast. Chiapas has a coastline along the Pacific Ocean to the south.
The Chixoy-Polochic Fault is a large, dominantly strike-slip, left-lateral fault runs largely parallel to the Motagua Fault situated some 80 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 Motagua Fault is a major, active left lateral-moving transform fault which cuts across Guatemala, continuing offshore along the southern Pacific coast of Mexico, returning onshore along the southernmost tip of Oaxaca, then continuing offshore until it merges with the Middle America Trench near Acapulco. It forms part of the tectonic boundary between the North American Plate and the Caribbean Plate. It is considered the onshore continuation of the Swan Islands Transform Fault which runs under the Caribbean Sea.
The Caribbean Sea is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico and Central America to the west and south west, to the north by the Greater Antilles starting with Cuba, to the east by the Lesser Antilles, and to the south by the north coast of South America.
The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America.
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.
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 of 7.5–7.8 Mw 1816 Guatemala earthquake 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 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. The fault display a 5 km to 10 km deep zone of microseismicity which may represent a locked zone. Only ≤ 5.6 Mw earthquakes have occurred on the fault since the beginning of regional instrumental records (1920 CE).
The moment magnitude scale is a measure of an earthquake's magnitude based on its seismic moment, expressed in terms of the familiar magnitudes of the original "Richter" magnitude scale.
The 1816 Guatemala earthquake occurred at 15:30 UTC on 22 July. It had an estimated magnitude of 7.5 to 7.75 on the Mw and a maximum perceived intensity of IX (Violent) on the Mercalli intensity scale. It was caused by movement on the Chixoy-Polochic Fault. The area affected by shaking up to intensity VII (Very strong) was at least 13,000 km2. At least 23 deaths were reported. The discovery of this earthquake 175 years after it occurred was based on study of historical documents, and is notable for showing that this portion of Guatemala, previously believed by many planners to be of low seismic risk, has experienced, and is at further risk of, very large earthquakes.
Before Present (BP) years is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred in the past. Because the "present" time changes, standard practice is to use 1 January 1950 as the commencement date of the age scale, reflecting the origin of practical radiocarbon dating in the 1950s. The abbreviation "BP" has alternatively been interpreted as "Before Physics"; that is, before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, making dating after that time likely to be unreliable.
Central America is located on the southern tip of North America, or is sometimes defined as a subcontinent of the Americas, bordered by Mexico to the north, Colombia to the southeast, the Caribbean Sea to the east, and the Pacific Ocean to the west and south. Central America consists of seven countries: Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama. The combined population of Central America has been estimated to be 41,739,000 and 42,688,190.
A transform fault or transform boundary is a plate boundary where the motion is predominantly horizontal. It ends abruptly and is connected to another transform, a spreading ridge, or a subduction zone.
The Cocos Plate is a young oceanic tectonic plate beneath the Pacific Ocean off the west coast of Central America, named for Cocos Island, which rides upon it. The Cocos Plate was created approximately 23 million years ago when the Farallon Plate broke into two pieces, which also created the Nazca Plate. The Cocos Plate also broke into two pieces, creating the small Rivera Plate. The Cocos Plate is bounded by several different plates. To the northeast it is bounded by the North American Plate and the Caribbean Plate. To the west it is bounded by the Pacific Plate and to the south by the Nazca Plate.
The Middle America Trench is a major subduction zone, an oceanic trench in the eastern Pacific Ocean off the southwestern coast of Middle America, stretching from central Mexico to Costa Rica. The trench is 1,700 miles (2,750 km) long and is 21,880 feet at its deepest point. The trench is the boundary between the Rivera, Cocos, and Nazca plates on one side and the North American and Caribbean plates on the other. It is the 18th-deepest trench in the world. Many large earthquakes have occurred in the area of the Middle America Trench.
The Mendocino Triple Junction (MTJ) is the point where the Gorda plate, the North American plate, and the Pacific plate meet, in the Pacific Ocean near Cape Mendocino in northern California. This triple junction is the location of a change in the broad plate motions which dominate the west coast of North America, linking convergence of the northern Cascadia subduction zone and translation of the southern San Andreas Fault system. The Gorda plate is subducting, towards N50ºE, under the North American plate at 2.5 – 3 cm/yr, and is simultaneously converging obliquely against the Pacific plate at a rate of 5 cm/yr in the direction N115ºE. The accommodation of this plate configuration results in a transform boundary along the Mendocino Fracture Zone, and a divergent boundary at the Gorda Ridge.
The Guatemalan Highlands is an upland region in southern Guatemala, lying between the Sierra Madre de Chiapas to the south and the Petén lowlands to the north. The highlands are made up of a series of high valleys enclosed by mountains. The local name for the region is Altos, meaning "highlands", which includes the northern declivity of the Sierra Madre. The mean elevation is greatest in the west and least in the east. A few of the streams of the Pacific slope actually rise in the highlands, and force a way through the Sierra Madre at the bottom of deep ravines. One large river, the Chixoy or Salinas River, escapes northwards towards the Gulf of Mexico. The relief of the mountainous country which lies north of the Highlands and drains into the Atlantic is varied by innumerable terraces, ridges and underfalls; but its general configuration is compared by E. Reclus with the appearance of "a stormy sea breaking into parallel billows". The parallel ranges extend east and west with a slight southerly curve towards their centres. A range called the Sierra de Chamá, which, however, changes its name frequently from place to place, strikes eastward towards Belize, and is connected by low hills with the Cockscomb Mountains; another similar range, the Sierra de Santa Cruz, continues east to Cape Cocoli between the Polochic and the Sarstoon; and a third, the Sierra de las Minas or, in its eastern portion, Sierra del Mico, stretches between the Polochic and the Motagua rivers. Between Honduras and Guatemala, the frontier is formed by the Sierra de Merendón.
The 1976 Guatemala earthquake struck on February 4 at 03:01:43 local time with a moment magnitude of 7.5. The shock was centered on the Motagua Fault, about 160 km northeast of Guatemala City at a depth of 5 kilometers (3.1 mi) near the town of Los Amates in the department of Izabal.
The Sierra de Chuacús is situated in the central highlands of Guatemala, and runs southeast from El Quiché to Baja Verapaz. Its northwestern border is marked by the Chixoy River basin in Uspantán, which separates it from the Sierra de los Cuchumatanes. Its eastern border is marked by the Salamá River which separates it from the Sierra de las Minas. Its southeastern border is defined by the Motagua River valley.
Nankai megathrust earthquakes are great megathrust earthquakes that occur along the Nankai megathrust – the fault under the Nankai Trough – which forms the plate interface between the subducting Philippine Sea Plate and the overriding Amurian Plate, which dips beneath southwestern Honshu, Japan. The fault is divided into five segments in three zones, which rupture separately or in combination, and depending on location, the resulting earthquakes are subdivided by zone from west to east into Nankai earthquakes, Tōnankai earthquakes, and Tōkai earthquakes.
The 2009 Swan Islands earthquake occurred on May 28 at 02:24:45 AM local time with a moment magnitude of 7.3 and a maximum Mercalli intensity of VII. The epicenter was located in the Caribbean Sea, 64 kilometres (40 mi) northeast of the island of Roatán, 19 miles northeast of Port Royal, Isla de Bahias, 15 miles northwest of Isla Barbaretta, and 130 kilometres (81 mi) north-northeast of La Ceiba. Three aftershocks followed the earthquake within magnitude 4 range.
Lake Chichoj is located near the city of San Cristóbal Verapaz, in the department of Alta Verapaz, in Guatemala. It is 1 km (0.62 mi) long, 0.5 km (0.31 mi) wide, with an area of 0.5 km2 (0.19 sq mi), an average water volume of 4.8 ± 0.1 m3 (169.5 ± 3.5 cu ft), and a maximum depth of 32 m (105 ft).
Cerro Amay is a mountain in the Quiché Department of Guatemala, centered near -90.77 W, 15.48 N. The mountain is affiliated with, but not part of, the Cuchumatanes Mountains, which lie to its west, and with the Sierra De Chama. Cerro Amay is topographically-distinct and is notable for the Cerro Amay Cloud Forest, a track of mostly virgin cloud forest covering approximately 19,000 hectare. Cerro Amay gets its name from Spanish and Kek'chi, a Mayan language. Cerro means 'mountain' and Amay means 'difficult to survive.' Cerro Amay has been little-studied by scientists because of its remoteness and the fact that few people know about it. Based upon geological maps, Cerro Amay is located directly on Chixoy-Polochic Geological Fault System that comprises the geological boundary between North America and South America., and is thus as close as possible to the site of the Great American Interchange. The Chixoy-Polochic Fault remains active and earthquakes are not uncommon, suggesting that Cerro Amay may still be growing. The highest point at Cerro Amay is approximately 2,615 meters above sea level. Cerro Amay is defined on its west side by the Putul River, and on its east side, the Chixoy River, which is the headwater of the Usumacinta. A steep southern escarpment defines the southern side of Cerro Amay and the north slopes gradually down to an elevation of approximately 700 meters above sea level. The largest city close to Cerro Amay is Uspantan, approximately 13 kilometers southwest of the southern escarpment of Cerro Amay.
The Swan Islands Transform Fault is a left-lateral (sinistral) strike-slip fault zone that forms part of the boundary between the Caribbean Plate and the North American Plate. It runs along the southern boundary of the Cayman Trough from the Mid-Cayman Rise spreading center in the east, to Guatemala in the west, where it continues as the Motagua Fault. It consists of two main fault strands that overlap west of the Swan Islands. It has been associated with several major earthquakes, including those in 2009 and 2018.
The Chortis Block is a 400–600 km (250–370 mi)-wide continental fragment in Central America located in the northwest corner of the oceanic Caribbean Plate.
The geology of Guatemala encompasses rocks divided into two tectonic blocks. The Maya Block in the north has igneous and metamorphic North American Craton basement rocks, overlain by late Paleozoic metasedimentary rocks, which experienced deformation during the Devonian. Red beds, evaporites and marine limestone from the Mesozoic overlie these rocks. A karst landscape formed in the thick limestone units across the north of the country. During a collisional orogeny, these Paleozoic and Mesozoic rocks were uplifted, thrusted and folded as the Central Guatemalan Cordillera. Paleogene rocks from the early Cenozoic include volcanic and marine clastic rocks, associated with high rates of erosion.
A geographic coordinate system is a coordinate system that enables every location on Earth to be specified by a set of numbers, letters or symbols. The coordinates are often chosen such that one of the numbers represents a vertical position and two or three of the numbers represent a horizontal position; alternatively, a geographic position may be expressed in a combined three-dimensional Cartesian vector. A common choice of coordinates is latitude, longitude and elevation. To specify a location on a plane requires a map projection.