The Motagua Fault (also, Motagua Fault Zone) 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.
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.
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.
The Motagua Fault is regarded by some geologists as part of a system of faults designated the "Motagua-Polochic system" rather than as a discrete single boundary. The Polochic fault (also referred to as the Chixoy-Polochic Fault) lies north and parallel to the Motagua Fault and shares some of the motion between the North American and Caribbean Plates.
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.
The Motagua Fault has been responsible for several major earthquakes in Guatemala's history, including the 7.5 Mw Guatemala 1976 earthquake.
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.
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.
Guatemala is mountainous, except for the south coastal area and the vast northern lowlands of Petén department. Two mountain chains enter Guatemala from west to east, dividing the country into three major regions: the highlands, where the mountains are located; the Pacific coast, south of the mountains; and the Petén region, north of the mountains. These areas vary in climate, elevation, and landscape, providing dramatic contrasts between hot and humid tropical lowlands and highland peaks and valleys.
The San Andreas Fault is a continental transform fault that extends roughly 1,200 kilometers (750 mi) through California. It forms the tectonic boundary between the Pacific Plate and the North American Plate, and its motion is right-lateral strike-slip (horizontal). The fault divides into three segments, each with different characteristics and a different degree of earthquake risk. The slip rate along the fault ranges from 20 to 35 mm /yr.
The Cayman Trough is a complex transform fault zone pull-apart basin which contains a small spreading ridge, the Mid-Cayman Rise, on the floor of the western Caribbean Sea between Jamaica and the Cayman Islands. It is the deepest point in the Caribbean Sea and forms part of the tectonic boundary between the North American Plate and the Caribbean Plate. It extends from the Windward Passage, going south of the Sierra Maestra of Cuba toward Guatemala. The transform continues onshore as the Motagua Fault, which cuts across Guatemala and extends offshore under the Pacific Ocean, where it intersects the Middle America Trench subduction zone.
The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust. The interior of the main continental landmass includes an extensive granitic core called a craton. Along most of the edges of this craton are fragments of crustal material called terranes, accreted to the craton by tectonic actions over a long span of time. It is thought that much of North America west of the Rocky Mountains is composed of such terranes.
The Gorda Plate, located beneath the Pacific Ocean off the coast of northern California, is one of the northern remnants of the Farallon Plate. It is sometimes referred to as simply the southernmost portion of the neighboring Juan de Fuca Plate, another Farallon remnant.
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 Puerto Rico Trench is located on the boundary between the Caribbean Sea and the Atlantic Ocean. The oceanic trench is associated with a complex transition between the Lesser Antilles subduction zone to the south and the major transform fault zone or plate boundary, which extends west between Cuba and Hispaniola through the Cayman Trough to the coast of Central America. The trench is 800 kilometres (497 mi) long and has a maximum depth of 8,376 metres (27,480 ft) or 5.20 miles in the Brownson Deep, which is the deepest point in the Atlantic Ocean and the deepest point not in the Pacific Ocean. On December 19, 2018, its deepest point was identified by the DSSV Pressure Drop using a state-of-the-art Kongsberg EM124 multibeam sonar and then directly visited and its depth verified by the manned submersible DSV Limiting Factor.
The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America.
The Motagua River is a 486-kilometre (302 mi) long river in Guatemala. It rises in the western highlands of Guatemala where it is also called Río Grande, and runs in an easterly direction to the Gulf of Honduras. The final few kilometres of the river form part of the Guatemala/Honduras border. The Motagua River basin covers an area of 12,670 square kilometres (4,890 sq mi) and is the largest in Guatemala.
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 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.
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.
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.