The 1957 Guerrero earthquake occurred on 28 July at 08:40 UTC. It had a magnitude of 7.6 and a maximum perceived intensity of VII (''very strong'') on the

Modified Mercalli intensity scale The Modified Mercalli intensity scale (MM, MMI, or MCS), developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. It measures the eff ...

Mexico City Mexico City ( es, link=no, Ciudad de México, ; abbr.: CDMX; Nahuatl: ''Altepetl Mexico'') is the capital and largest city of Mexico, and the most populous city in North America. One of the world's alpha cities, it is located in the Valley o ...

and

Chilpancingo Chilpancingo de los Bravo (commonly shortened to Chilpancingo; ; Nahuatl: Chilpantsinko) is the capital and second-largest city of the state of Guerrero, Mexico. In 2010 it had a population of 187,251 people. The municipality has an area of in ...

were particularly badly affected. It caused the deaths of between 54 and 160 people. A small

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explo ...

was triggered but caused little damage.

Tectonic setting

The state 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 ...

lies adjacent to part of the

Middle America Trench 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 an ...

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 ...

beneath 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 Pacific ...

. The convergence between these plates at this location is about 65 mm per year. There have been many large and destructive earthquakes in the past, such as the M 7.6 1911 Guerrero earthquake. The Guerrero

seismic gap A seismic gap is a segment of an active fault known to produce significant earthquakes that has not slipped in an unusually long time, compared with other segments along the same structure. There is a hypothesis or theory that states that over long ...

is a ca. 200 km long segment of the subduction interface, which has not had a large earthquake since the 1911 event. Although several

slow earthquake A slow earthquake is a discontinuous, earthquake-like event that releases energy over a period of hours to months, rather than the seconds to minutes characteristic of a typical earthquake. First detected using long term strain measurements, most ...

s have been observed in that time interval, an earthquake in the range M 7.9–8.0 could still be expected within the Guerrero gap.

Earthquake

The earthquake originally had an estimated magnitude of 7.9 . This was recalculated by the

International Seismological Centre The International Seismological Centre (ISC) is a non-governmental, nonprofit organisation charged with the final collection, definitive analysis and publication of global seismicity. The ISC was formed in 1964 as an international organisation ...

in their ISC-GEM catalogue as 7.6 . The duration of strong shaking was recorded as 90 seconds in Mexico City. The earthquake is thought to have ruptured the plate interface at the southeastern end of the Guerrero seismic gap.

Damage

The greatest damage was observed in Mexico City, where many buildings were destroyed. Chilpancingo was also badly affected with 90% of buildings being damaged. The towns of Ayutla, Chilapa,

Huamuxtitlán Huamuxtitlán is a city and seat of the municipality of Huamuxtitlán, in the state of Guerrero, south-western Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. ...

, San Luis Acatlan,

San Marcos San Marcos is the Spanish name of Saint Mark. It may also refer to: Towns and cities Argentina * San Marcos, Salta Colombia * San Marcos, Antioquia * San Marcos, Sucre Costa Rica * San Marcos, Costa Rica (aka San Marcos de Tarrazú) ...

Tlapa Tlapa de Comonfort, often shortened to Tlapa and known as Tinda'i in Mixtec, is a city in the mountain region of the Mexican state of Guerrero. It also serves as the municipal seat for the surrounding municipality of the same name. "Tlapa" is a ...

and Huitzuco all sustained significant damage.

References

{{Earthquakes in Mexico 1957 earthquakes Earthquakes in Mexico July 1957 events in Mexico 1957 in Mexico 1957 disasters in Mexico

Tectonic setting

Earthquake

Damage

See also

References