The 2012 Guerrero–Oaxaca earthquake struck southern

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 ...

with a

moment magnitude The moment magnitude scale (MMS; denoted explicitly with or Mwg, and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment. was defined in a 1979 paper ...

of 7.4 at on Tuesday, 20 March. Its

epicenter The epicenter (), epicentre, or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates. Determination The primary purpose of a ...

was near

Ometepec Ometepec is a city and the seat of the municipality of Ometepec, in the southern Mexican state of Guerrero.Instituto Nacional de Estadística y Geografía The National Institute of Statistics and Geography (INEGI from its former name in ...

, in the border between the states of

Guerrero Guerrero, officially the Free and Sovereign State of Guerrero, is one of the 32 states that compose the administrative divisions of Mexico, 32 Federal Entities of Mexico. It is divided into Municipalities of Guerrero, 85 municipalities. The stat ...

and

Oaxaca Oaxaca, officially the Free and Sovereign State of Oaxaca, is one of the 32 states that compose the political divisions of Mexico, Federative Entities of the Mexico, United Mexican States. It is divided into municipalities of Oaxaca, 570 munici ...

. With a shallow

focus Focus (: foci or focuses) may refer to: Arts * Focus or Focus Festival, former name of the Adelaide Fringe arts festival in East Australia Film *Focus (2001 film), ''Focus'' (2001 film), a 2001 film based on the Arthur Miller novel *Focus (2015 ...

of 20 km, the earthquake caused strong shaking over a large area along the Oaxaca–Guerrero border and the adjacent Pacific coastline. Significant tremors were felt in areas up to several hundred kilometers away, including

Mexico City Mexico City is the capital city, capital and List of cities in Mexico, largest city of Mexico, as well as the List of North American cities by population, most populous city in North America. It is one of the most important cultural and finan ...

and also 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 ...

. Two people were killed and over 30,000 houses were damaged or destroyed.

Tectonic setting

The states of Guerrero and Oaxaca lie above the

convergent boundary A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a ...

where the Cocos plate is being

subducted Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second plat ...

below the North American plate at a rate of 6.4 cm/yr (2.5 in/yr). The dip of the subducting slab is about 15° as defined by

focal mechanism The focal mechanism of an earthquake describes the Fault (geology)#Slip.2C heave.2C throw, deformation in the Hypocenter, source region that generates the seismic waves. In the case of a Fault (geology), fault-related event, it refers to the ori ...

s and

hypocenter A hypocenter or hypocentre (), also called ground zero or surface zero, is the point on the Earth's surface directly below a nuclear explosion, meteor air burst, or other mid-air explosion. In seismology, the hypocenter of an earthquake is its ...

s of previous earthquakes. Seismicity in this area is characterized by regular

megathrust earthquake Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthq ...

s along the plate interface. In addition, there have been a series of historic

normal fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

events within the subducting slab.

Earthquake

According to the

National Seismological Service The National Seismological Service (, SSN) is a seismological organization in Mexico that studies and records earthquake activity within the country. It is part of the Geophysics Institute at the National Autonomous University of Mexico (UNAM) and ...

(NSS) of Mexico, the

was located in the Oaxaca-Guerrero border, about 30 km south of Ometepec and 8 km southeast of Cuajinicuilapa. The

United States Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on Mar ...

(USGS) reported the epicenter in the state of

, about 23 km east of Ometepec and 6 km northwest of

San Juan Cacahuatepec San Juan Cacahuatepec is a city in the Mexican state of Oaxaca, near the border with Guerrero. It is located in the Jamiltepec District in the west of the Costa Region. Its population in 1990, according to ''The Columbia Gazetteer of North Americ ...

. The depth was reported as 15 km by NSS and 20 km by the USGS. The slip of the earthquake was compactly distributed in an area of about 30 km × 30 km. The focal mechanism and depth of the earthquake indicate that it was a result of

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. I ...

ing along or close to the plate interface. Similar earthquakes have struck the area before, including the 1932 Jalisco earthquake, the

1985 Mexico City earthquake The 1985 Mexico City earthquake struck in the early morning of 19 September at 07:17:50 (CST) with a Moment magnitude scale, moment magnitude of 8.0 and a maximal Modified Mercalli intensity scale, Mercalli intensity of IX (''Violent''). The ev ...

, the

1995 Colima–Jalisco earthquake The 1995 Colima–Jalisco earthquake occurred on October 9 at 15:35 UTC with a moment magnitude of 8.0 and a maximum Mercalli intensity of VIII (''Severe''). The shock occurred off the coast of Jalisco, Mexico, where a tsunami was triggered that a ...

and the

2003 Colima earthquake An earthquake struck the Pacific Coast of Mexico on 21 January 2003 with a moment magnitude of 7.5. It had a maximum Mercalli intensity of VIII (''Severe''). The epicenter was located on the Pacific coast near the Mexican state of Colima. The ea ...

. The earthquake coincided with an earthquake drill in Chiapas. The earthquake drill, simulating an earthquake of magnitude 7.9 on the Richter scale, was implemented by the Protección Civil of Chiapas on 20 March. The earthquake drill started at 12:00, and the real earthquake occurred just minutes later.

Damage

The airport of Mexico City was closed for a short time and reopened after no damage had been observed. The trading of

Mexican Stock Exchange The Mexican Stock Exchange (), commonly known as Mexican Bolsa, Mexbol, or BMV, is one of two stock exchanges in Mexico, the other being BIVA - Bolsa Institucional de Valores. It is the second largest stock exchange in Latin America, only after S ...

(BMV) was suspended. The earthquake caused power outage in central and eastern Mexico and affected 2.5 million users according to

Comisión Federal de Electricidad The Comisión Federal de Electricidad () is the Government-owned company, state-owned electric utility of Mexico, widely known as CFE. The Mexican Constitution of Mexico, constitution states that the government is responsible for the control and ...

(CFE). On 22 March it was announced that two people were killed in Cuajinicuilapa because of the earthquake, one direct and one indirect. The first died due to the injuries caused after a wall collapsed on him in El Tamale community, while the second suffered a heart attack, in San Nicolás.

Intensity

The earthquake struck during the midday in a moderately populated region, with a mix of earthquake-resistant and vulnerable structures. The strongest ground motions registered at very strong (MM VII) on the

Mercalli intensity scale The Modified Mercalli intensity scale (MM, MMI, or MCS) measures the effects of an earthquake at a given location. This is in contrast with the seismic magnitude usually reported for an earthquake. Magnitude scales measure the inherent force or ...

, affecting smaller cities and towns near the epicenter such as

, Cuajinicuilapa,

and

Pinotepa Nacional Pinotepa Nacional (formally: Santiago Pinotepa Nacional; in Ñu'savi, ''Ñuu Ñoko'', which means Twenty-House Town) is a city and seat of the municipality of the same name, in the Mexican state of Oaxaca. It is located in the Jamiltepec Distric ...

. Many other areas in the states of Guerrero and Oaxaca experienced strong (MM VI) shaking, while larger cities—such as Huajuapan de León, Oaxaca, Tehuacán, Puebla, and

Acapulco, Guerrero Acapulco de Juárez (), commonly called Acapulco ( , ; ), is a city and major seaport in the state of Guerrero on the Pacific Coast of Mexico, south of Mexico City. Located on a deep, semicircular bay, Acapulco has been a port since the ear ...

—experienced moderate (MM V) tremors. Lighter ground motions(MM IV–III)spread through much of south-central Mexico. The earthquake could be felt in the federal entities of Guerrero,

State of Mexico The State of Mexico, officially just Mexico, is one of the 32 federal entities of the United Mexican States. Colloquially known as Edomex (from , the abbreviation of , and ), to distinguish it from the name of the whole country, it is the mo ...

, Morelos, Querétaro, Michoacán, Puebla, Tabasco, Tlaxcala, Hidalgo, Oaxaca, Chiapas,

Veracruz Veracruz, formally Veracruz de Ignacio de la Llave, officially the Free and Sovereign State of Veracruz de Ignacio de la Llave, is one of the 31 states which, along with Mexico City, comprise the 32 Political divisions of Mexico, Federal Entit ...

Colima Colima, officially the Free and Sovereign State of Colima, is among the 31 states that make up the 32 Federal Entities of Mexico. It shares its name with its capital and main city, Colima. Colima is a small state of western Mexico on the cen ...

Jalisco Jalisco, officially the Free and Sovereign State of Jalisco, is one of the 31 states which, along with Mexico City, comprise the 32 Political divisions of Mexico, Federal Entities of Mexico. It is located in western Mexico and is bordered by s ...

, San Luís Potosí,

Guanajuato Guanajuato, officially the Free and Sovereign State of Guanajuato, is one of the 32 states that make up the Political divisions of Mexico, Federal Entities of Mexico. It is divided into Municipalities of Guanajuato, 46 municipalities and its cap ...

Campeche Campeche, officially the Free and Sovereign State of Campeche, is one of the 31 states which, with Mexico City, make up the Administrative divisions of Mexico, 32 federal entities of Mexico. Located in southeast Mexico, it is bordered by the sta ...

, and

Sinaloa Sinaloa (), officially the (), is one of the 31 states which, along with Mexico City, compose the Federal Entities of Mexico. It is divided into 18 municipalities, and its capital city is Culiacán Rosales. It is located in northwest Mexic ...

of Mexico, and also in

. The intensity in Mexico City was MM VI–VII, which was stronger than the surrounding area because of local topography and soil conditions. Part of a pedestrian bridge collapsed on a small passenger bus in

Azcapotzalco Azcapotzalco ( ; ; from ''wikt:azcapotzalli, āzcapōtzalli'' “anthill” + ''wikt:-co, -co'' “place”; literally, “In the place of the anthills”) is a Boroughs of Mexico City, borough (''demarcación territorial'') in Mexico City. Azcap ...

, Mexico City, with no injuries reported. The service of Mexico City Metro Line A was interrupted because of track damage.

Aftershocks

Multiple

aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in Epicenter, the same area of the Mainshock, main shock, caused as the displaced Crust (geology), crust adjusts to the effects of the main shock. Large earthq ...

s have been reported in the Guerrero–Oaxaca region. According to the NSS, 828 aftershocks have occurred, the strongest of them was felt on 2 April 2012. It was a magnitude 6.0 M_W earthquake that struck at 12:36 local time (18:36 UTC).

Aftermath

According to Asociación Mexicana de Instituciones de Seguros (AMIS), it was estimated that insurance companies would have to pay 2.07 billion pesos ($100.9 million

USD The United States dollar (symbol: $; currency code: USD) is the official currency of the United States and several other countries. The Coinage Act of 1792 introduced the U.S. dollar at par with the Spanish silver dollar, divided it int ...

) due to the earthquake. 80% of the loss was concentrated in Guerrero, followed by Mexico City, Oaxaca, and Puebla.

References

External links

M7.4 – Oaxaca, Mexico
–

* {{DEFAULTSORT:2012 Guerrero-Oaxaca Earthquake Guerrero-Oaxaca earthquake Earthquakes in Mexico 21st century in Guerrero History of Oaxaca Guerrero-Oaxaca Earthquake March 2012 in North America 2012 disasters in Mexico