The 2012 Guerrero–Oaxaca earthquake struck southern

Mexico Mexico (Spanish: México), 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 Guatema ...

with a

moment magnitude The moment magnitude scale (MMS; denoted explicitly with or Mw, 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. It was defined in a 1979 pape ...

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. Surface damage Before the instrumental pe ...

was near

Ometepec Ometepec is a city and the seat of the municipality of Ometepec, in the state of Guerrero, south-western Mexico Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in ...

, in the border between the states of

Guerrero Guerrero is one of the 32 states that comprise the 32 Federal Entities of Mexico. It is divided in 81 municipalities and its capital city is Chilpancingo and its largest city is Acapulcocopied from article, GuerreroAs of 2020, Guerrero the pop ...

and

Oaxaca Oaxaca ( , also , , from nci, Huāxyacac ), officially the Free and Sovereign State of Oaxaca ( es, Estado Libre y Soberano de Oaxaca), is one of the 32 states that compose the political divisions of Mexico, Federative Entities of Mexico. It is ...

. With a shallow

focus Focus, or its plural form foci may refer to: Arts * Focus or Focus Festival, former name of the Adelaide Fringe arts festival in South Australia Film *''Focus'', a 1962 TV film starring James Whitmore * ''Focus'' (2001 film), a 2001 film based ...

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 ( es, link=no, Ciudad de México, ; abbr.: CDMX; Nahuatl: ''Altepetl Mexico'') is the capital city, capital and primate city, largest city of Mexico, and the List of North American cities by population, most populous city in North Amer ...

and also in Guatemala. 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 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 ...

is being

subducted Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

below the

North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacif ...

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 mechanisms and

hypocenter In seismology, a hypocenter or hypocentre () is the point of origin of an earthquake or a subsurface nuclear explosion. A synonym is the focus of an earthquake. Earthquakes An earthquake's hypocenter is the position where the strain energy ...

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 earthqu ...

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 tecton ...

events within the subducting slab.

Earthquake

According to the National Seismological Service (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), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

(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 Amer ...

. 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. If ...

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

1932 Jalisco earthquake The 1932 Jalisco earthquakes began on June 3 at 10:36 UTC with a megathrust event that registered 8.1 on the moment magnitude scale. With a maximum perceived intensity of X (''Extreme'') on the Mercalli intensity scale, at least 400 deaths were ...

, 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 of 8.0 and a maximal Mercalli intensity of IX (''Violent''). The event caused serious damage to the Greater Mexico City area ...

, the 1995 Colima–Jalisco earthquake and the

2003 Colima earthquake The 2003 Colima earthquake occurred on 21 January with a moment magnitude of 7.6 and a maximum Mercalli intensity of VIII (''Severe''). The epicenter was located on the Pacific coast in the Mexican state of Colima. The earthquake was felt as far ...

. 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 ( es, Bolsa Mexicana de Valores), 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 ...

(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 (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, affecting smaller cities and towns near the epicenter such as

, Cuajinicuilapa,

and

Pinotepa Nacional Pinotepa Nacional (formally: Santiago Pinotepa Nacional; in Mixtec, ''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 District ...

. 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 ( , also , nah, Acapolco), is a city and major seaport in the state of Guerrero on the Pacific Coast of Mexico, south of Mexico City. Acapulco is located on a deep, semicircular bay and has bee ...

—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, 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 ( es, Estado Libre y Soberano de Veracruz de Ignacio de la Llave), is one of the 31 states which, along with Me ...

Colima Colima (), officially the Free and Sovereign State of Colima ( es, Estado Libre y Soberano de Colima), is one of the 31 states that make up the 32 Federal Entities of Mexico. It shares its name with its capital and main city, Colima. Colima i ...

, Jalisco, San Luís Potosí, Guanajuato, Campeche, and Sinaloa of Mexico, and also in Guatemala. 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 ( nci, Āzcapōtzalco , , from '' āzcapōtzalli'' “anthill” + '' -co'' “place”; literally, “In the place of the anthills”) is a borough (''demarcación territorial'') in Mexico City. Azcapotzalco is in the northwestern p ...

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

Aftershocks

Multiple aftershocks 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: $; code: USD; also abbreviated US$ or U.S. Dollar, to distinguish it from other dollar-denominated currencies; referred to as the dollar, U.S. dollar, American dollar, or colloquially buck) is the official ...

) 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
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* {{DEFAULTSORT:2012 Guerrero-Oaxaca Earthquake Guerrero-Oaxaca earthquake Earthquakes in Mexico History of Guerrero History of Oaxaca Guerrero-Oaxaca Earthquake March 2012 events in North America 2012 disasters in Mexico