The Chiapas Earthquake, Mexico 2017
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GEOFILE Extension 781 The Chiapas earthquake, Mexico 2017 By Philippa Simmons Synopsis Links This Geofile will explore the causes and impacts of Exam board Link to specification the Chiapas earthquake that occurred in Mexico in AQA September 2017, as well as the responses to it. Mexico AS Component 1 Physical Geography 3.3.1.4 is situated where the Cocos plate converges with the Seismic hazards p18 pdf version North American plate – one of the most tectonically Click here active regions in the world, with up to 40 earthquakes A2 Component 1 Physical Geography 3.1.5.4 a day. The state of Chiapas is located along the Seismic hazards p15 pdf version Click here southern shore of Mexico and borders Guatemala, it is in a subduction zone and is at risk of strong Edexcel AS 1.4c and 1.5c Social and economic impacts of earthquakes. At 23.49 local time on 7 September 2017 tectonic hazards p18 pdf version an earthquake of magnitude 8.2 struck off the coast of Click here Mexico. This was the strongest earthquake to be A2 1.4c and 1.5c Social and economic impacts of recorded globally in 2017, resulting in it being the tectonic hazards p15 pdf version Click here second strongest ever in Mexico. OCR AS Topic 2.5 Hazardous Earth 4b Range of impacts Key terms on people as a result of earthquake activity – Tectonic, tectonic hotspot, plate boundary, case studies convergent boundary, aftershock, magnitude, + 5b Strategies – case studies tsunami, vulnerability. p39 pdf version Click here Learning objectives A2 Topic 3.5 Hazardous Earth 4b There is a range of impacts people experience as a result of After working through this Geofile you should have earthquake activity – case studies learned about: + 5b There are various strategies to manage hazards from earthquakes – case studies ●● the causes of the Chiapas earthquake p51 pdf version ●● the impact of the earthquake, particularly focusing Click here on the people in Chiapas who live in an emerging Eduqas A2 3.1.3 Earthquakes, processes, hazards and their economy impacts 3.1.4 Human factors affecting risk and ●● the nature of the responses to the earthquake from vulnerability the Mexican government 3.1.5 Responses to tectonic hazards ●● the work Mexico still needs to do to improve its P30 of pdf version earthquake preparedness. Click here WJEC AS 1.3.3 Earthquakes, processes, hazards and their impacts 1.3.4 Human factors affecting risk and vulnerability 1.3.5 Responses to tectonic hazards P20 pdf version Click here A2 4.1.3 Earthquakes, processes, hazards and their impacts 4.1.4 Human factors affecting risk and vulnerability 4.1.6 Responses to earthquakes P35 pdf version Click here © Oxford University Press 2019 GeoFile, Series 37 Issue 2, January 2019 1 GEOFILE Extension ● 781 The Chiapas earthquake, Mexico 2017 Mexico – a tectonic breaking point, at which point the million people felt it and it even hotspot upper plate will spring back, lifting caused buildings to sway as far Mexico is situated in a tectonically the ocean floor. Consequently the away as Mexico City (Figure 1). region of Chiapas is at risk of both active area and its inhabitants are Earthquakes are a common large earthquakes and tsunamis. used to regular seismic activity, such occurrence in Mexico (Figure 2), as the devastating earthquake that but the causes behind the Chiapas struck Mexico City in 1985. It The causes of the earthquake were complex. One measured 8.1 on the Richter scale Chiapas earthquake factor was the depth of the and destroyed 100,000 buildings. On 7 September 2017 an earthquake, 70km, deep off the Over 5,000 people died and millions earthquake with a magnitude of southern coast of Mexico. This were left without electricity or fresh 8.2 M , as recorded by the USGS, indicated that the earthquake most w water. The earthquake was so hit shortly before midnight off the probably happened within the catastrophic because Mexico City lies southern coast of Mexico, 100 miles plate, as opposed to at the on a former lake-bed, which results (160 km) from the Chiapas region subduction zone between the North in any earthquake being amplified (Figure 1). Approximately 90 people American and Cocos plates. The by the soft alluvial soil. Research has were killed and great damage was Cocos plate is made up of crust shown that the shaking of the caused to the coastal areas around beneath the Pacific Plate and is 1985 earthquake could have been the epicentre. There was a mass sinking deeper into the earth under amplified by as much as 500%. The evacuation from the coast due to its own weight. It would seem that 1985 earthquake also demonstrated initial tsunami warnings. The this is causing fractures inside the that many buildings in the capital, intensity of the earthquake was so slab bend (Figure 3). Geologists particularly in the informal great that it was stated that nearly believe this could have been the settlements, were not earthquake- half of Mexico’s population of 120 cause of the 2017 earthquake. resistant. In response to this, the Mexican government has put a lot of resources into improving the infrastructure in the country’s main cities. Mexico lies between three tectonic plates: the Pacific, North American and Cocos plates. This not only makes it one of the most seismically active countries in the world, but also leaves it vulnerable to volcanic eruptions. The region of Chiapas lies on the boundary of the Cocos and North American plates. At this convergent plate boundary, the oceanic Cocos plate is being forced below the continental North American plate. This creates a subduction zone due to the Figure 1 The Chiapas earthquake oceanic plate being denser than the continental plate. Converging plate Date Affected Area Magnitude Deaths Injuries boundaries can be the cause of very 23 September 2017 Oaxaca 6.1 M 6 7 large earthquakes, and because the w 19 September 2017 Mexico City, Morelos, 7.1 Mw 370 6,011 Cocos plate is being subducted, the Puebla two plates can lock, resulting in 7 September 2017 Chiapas, Oaxaca 8.2 Mw 98 300 pressure building up. The pressure will build up until it reaches a Figure 2 Notable earthquakes in Mexico, 2017 © Oxford University Press 2019 GeoFile, Series 37 Issue 2, January 2019 2 GEOFILE Extension The Chiapas earthquake, Mexico 2017 ● 781 Impacts of the earthquake Following the earthquake the main areas that were affected were the neighbouring states of Chiapas, Oaxaca and Tabasco, around the epicentre. The earthquake had the following initial impacts: ●● 1.5 million people were affected. ●● In the state of Chiapas the earthquake caused damage to 41,000 homes ●● Approximately 90 people who were killed – 71 in Oaxaca, four in Tabasco and 15 in Chiapas. ●● At least 1 million people were left without electricity Figure 3 Section across the Cocos oceanic plate immediately following the earthquake, and later around There is still a lot of research to be earthquake, the Pacific Tsunami 800,000 people. done, due to the complexity of this Warning Centre issued a warning ●● Following the earthquake, tectonic zone. for the whole of the Central schools were closed in 11 American Pacific coast. It was different states to check the Tsunami hazard originally thought there could be safety of the buildings. tsunami waves of up to 3 m high Earthquakes can cause secondary ●● The states of Chiapas and Oaxaca along the coast of Mexico, but it was impacts, the most devastating of are two of the poorest states in later recorded that there were only these often being a tsunami, such as Mexico and many of the waves as high at 0.7 m along the the one that followed Japan’s 2011 communities are not only poor coast. The warning allowed time for Tohuku earthquake. Tsunamis are but also isolated. Many buildings some coastal communities to commonly created at subduction collapsed due to being made out evacuate as a precaution; eventually zones, due to the amount of of flimsy material which was the warnings were lifted, when the pressure that can build up between easily destroyed. lower threat was realised. the two plates. When this pressure ●● There were reports of buildings is released, it is often in the form of Following the tsunami warning, swaying in Mexico City, and a the overriding plate snapping back, there were a number of aftershocks highway bridge which was under which displaces the water above it, from the initial earthquake. construction near Mexico City’s creating a tsunami. The Chiapas Aftershocks are smaller earthquakes international airport collapsed earthquake was different and was which usually only last a few due to the shaking. due to stresses caused by gravity seconds and happen as the earth’s bending and dragging the Cocos crust is adjusting to the effects of Responses to the earthquake plate into the earth. It created a the main shock. In the hour Public officials were quick to give tsunami due to it being on a normal following the earthquake, at least guidance following the earthquake, fault (Figure 3), where the plate 12 aftershocks were recorded by one of the biggest since the 1985 drops down. This was similar to the the United States Geological Mexico City event. Samoa 2009 earthquake, which Service, and in the week following The Mexican government had caused a much larger tsunami. the earthquake a further 1800 learnt a lot from the 1985 aftershocks occurred, some having The tsunami was smaller for the earthquake, when many residents a magnitude of up to 6.1 on the Chiapas earthquake because it had been trapped under rubble, Richter scale.