Earthquake – Mexican Routes

How often does Mexico have earthquakes?

admin — Wed, 27 Sep 2023 22:45:36 +0000

Earthquakes are a natural phenomenon that occurs all over the world, and Mexico is no exception. Are earthquakes common in Mexico? Indeed, Mexico experiences very strong earthquakes with far-reaching consequences.

Earthquakes greater than magnitude 8 destroy numerous homes within a radius of several hundred kilometers and cause great damage and devastation. However, earthquakes of this magnitude occur relatively infrequently.

Why does Mexico have so many earthquakes?

Mexico is located in a seismically active region, primarily due to its location along the Pacific Ring of Fire. This area is notorious for its tectonic plate boundaries, where multiple plates interact, resulting in frequent seismic activity.

When discussing the frequency of earthquakes, understanding the concept of magnitude is crucial.

Magnitude measures the energy released at the source of an earthquake. Mexico experiences earthquakes of varying magnitudes, from minor tremors to more significant events. This diversity contributes to the overall frequency of seismic activity.

To understand the frequency of earthquakes in Mexico, let’s look at some statistics. On average, Mexico experiences thousands of earthquakes each year. However, most of these are low magnitude and often go unnoticed by the population.

The frequency of earthquakes in Mexico is closely related to its geological location. Public awareness and education are key components in mitigating the impact of these natural phenomena on communities across the country.

How many earthquakes does Mexico experience per year?

Mexico experiences 40-50 earthquakes per year, mostly below magnitude 5.

Most earthquakes in Mexico occur along the boundaries of the Cocos Plate, which is subducting beneath the North American Plate. The subduction zone is located off the southwest coast of Mexico, particularly near Guerrero and Oaxaca.

These earthquakes are felt in the central parts of the country, including Mexico City. The geological and topographic conditions in central Mexico, where the capital is located, are conducive to the propagation of seismic waves.

Mexico City, like many other urban areas in Mexico located in seismically active regions, experiences a certain number of earthquakes each year. The frequency can vary, and not all earthquakes are noticeable or significant.

The biggest earthquakes in Mexico history

Mexico has had significant seismic events in its history, such as the devastating 1985 Mexico City earthquake. Analysis of these past events sheds light on the region’s vulnerability to seismic activity.

Several factors contribute to the frequency of earthquakes in Mexico.

Subduction zones, where one tectonic plate slides beneath another, are common in the region. Additionally, complex interactions between the Cocos Plate and the North American Plate play a critical role in the observed seismic activity.

21 century:

22.09.2022 – Michoacán – 6.8 Mw
19.09.2022 – Michoacán – 7.6 Mw
21.06.2022 – Jalisco – 2.4 Mw
03.03.2022 – Veracruz – 5.7 Mw
07.09.2021 – Guerrero – 7.0 Mw
23.06.2020 – Oaxaca – 7.4 Mw
16.02.2018 – Oaxaca – 7.2 Mw
23.09.2017 – Oaxaca – 6.1 Mw
19.09.2017 – Mexico City, Morelos, Puebla – 7.1 Mw
07.09.2017 – Chiapas, Oaxaca – 8.2 Mw
23.11.2015 – Guerrero – 5.5 Mw
07.07.2014 – Chiapas – 6.9 Mw
08.05.2014 – Guerrero – 6.6 Mw
18.04.2014 – Guerrero – 7.2 Mw
20.03.2012 – Guerrero, Oaxaca – 7.4 Mw
10.12.2011 – Guerrero – 6.5 Mw
05.05.2011 – Guerrero – 5.7 Mw
30.06.2010 – Oaxaca – 6.2 Mw
04.04.2010 – Baja California – 7.2 Mw
27.04.2009 – Guerrero – 5.8 Mw
22.01.2003 – Colima – 7.5 Mw

20 century:

29.12.1999 – Guerrero – 5.9 Mw
30.09.1999 – Oaxaca – 7.4 Mw
15.06.1999 – Puebla – 7.0 Mw
11.01.1997 – Michoacán – 7.2 Mw
21.10.1995 – Chiapas – 7.1 Mw
09.10.1995 – Colima, Jalisco – 8.0 Mw
14.09.1995 – Guerrero – 7.4 Mw
25.04.1989 – Guerrero – 6.9 Mw
19.09.1985 – Michoacán, Mexico City – 8.0 Mw
25.10.1981 – Michoacán – 7.2 Mw
24.10.1980 – Oaxaca – 7.2 Mw
15.10.1979 – Baja California – 6.4 Mw
14.03.1979 – Guerrero – 7.6 Mw
28.08.1973 – Puebla, Veracruz – 7.1 ML
30.01.1973 – Colima – 7.5 Ms
02.08.1968 – Guerrero, Oaxaca – 7.3
23.08.1965 – Oaxaca – 7.5 Mw
06.07.1964 – Guerrero – 7.4 Ms
26.08.1959 – Veracruz – 6.4 Mw
28.07.1957 – Guerrero, Mexico City – 7.9 Ms
15.04.1941 – Colima – 7.6 Mw
26.07.1937 – Puebla, Veracruz – 7.3 Ms
22.06.1932 – Colima – 7.0 Mw
18.06.1932 – Colima – 7.8 Mw
03.06.1932 – Jalisco – 8.1 Mw
15.01.1931 – Oaxaca – 7.8 Mw
03.01.1920 – Puebla, Veracruz – 6.4 Ms
19.11.1912 – State of Mexico – 7.0
16.12.1911 – Guerrero – 7.6
07.06.1911 – Michoacán – 7.6
30.07.1909 – Guerrero – 7.6
15.04.1907 – Guerrero – 7.7
20.01.1900 – Colima – 7.4

19 century:

24.01.1899 – Guerrero – 7.5
05.06.1897 – Oaxaca – 7.4
02.11.1894 – Guerrero, Oaxaca – 7.4
24.02.1892 – Baja California – 7.1–7.2
02.12.1890 – Guerrero, Oaxaca – 7.3
06.09.1889 – Guerrero – 7.1
29.05.1887 – Guerrero – 7.3
03.05.1887 – Sonora – 7.6 Mw
19.07.1882 – Guerrero, Oaxaca – 7.5
17.05.1879 – Puebla – 7.1
09.03.1875 – Colima, Jalisco – 7.4
11.02.1875 – Jalisco – 7.5
16.03.1874 – Guerrero – 7.3
27.03.1872 – Oaxaca – 7.4
11.05.1870 – Oaxaca – 7.8
03.10.1864 – Puebla, Veracruz – 7.3
19.06.1858 – Michoacán – 7.5
05.05.1854 – Oaxaca – 7.7
04.12.1852 – Acapulco – 7.8
07.04.1845 – Guerrero – 7.9 Ms
29.11.1852 – Baja California – 6.5 MLa
09.03.1845 – Oaxaca – 7.5
22.11.1837 – Jalisco – 7.7
06.01.1835 – State of Mexico –
04.05.1820 – Guerrero – 7.6
31.05.1818 – Colima, Michoacán – 7.7
25.03.1806 – Colima, Michoacán – 7.5 Ms
08.03.1800 – Central, Eastern, and Southeastern –

18 century:

28.03.1787 – Guerrero, Oaxaca, Mexico City – 8.6 Mw

Twin earthquakes in Mexico City

There are two major earthquakes in the collective memory of Mexicans: one in 1985 and one in 2017. At 13:19 on September 19, 1985, Mexico woke up to the most destructive earthquake in its modern history.

September 19, 1985 – Mexico City earthquake

On September 19, 1985, at 7:17, Mexico was struck by a devastating earthquake that left an indelible mark on the country’s history. The magnitude 8.1 seismic event struck central Mexico, including Mexico City.

Thousands were killed and buildings and infrastructure were damaged.

The magnitude of the earthquake contributed to its destructiveness, collapsing buildings and causing widespread panic. The aftermath prompted a review of building codes and disaster preparedness measures in Mexico.

The aftermath of the 1985 earthquake prompted an outpouring of national and international support. The recovery efforts were challenging, but they resulted in improved infrastructure and disaster response mechanisms.

September 19, 2017 – Mexico City earthquake

Exactly 32 years later, on September 19, 2017, at 13:14, another powerful earthquake of magnitude 7.1 struck Mexico. This time, the earthquake hit the central Mexican states of Puebla, Morelos, and Mexico City.

This earthquake occurred just two hours after the annual national earthquake preparation, the “Mega Simulacro” (Mega Drill), and tragically, the new earthquake occurred on the same day as the 1985 earthquake.

Once again, just like 32 years ago, buildings collapsed and people died tragically.

September 19, 2022 – Mexico earthquake

The earthquakes that struck Mexico City on September 19, 1985, and September 19, 2017, were significant in the country’s history. On September 22, 2022, Mexico was hit by another significant earthquake.

A magnitude 7.6 earthquake struck western Mexico on the anniversary of two devastating earthquakes in 1985 and 2017. The quake struck shortly after 13:00 local time near the border of Michoacan with the state of Colima.

This earthquake was relatively shallow, only 15 km deep, which amplified its impact and led to a tsunami warning being issued. However, no major damage was reported in Mexico City following the quake.

The National Autonomous University of Mexico (UNAM) said there was no scientific explanation for three major earthquakes occurring on the same day, blaming it on pure coincidence.

Earthquake safety measures in Mexico

Given the seismic nature of the region, Mexico has invested in earthquake monitoring systems. Organizations such as the National Seismological Service play an important role in tracking seismic events and providing early warnings.

This proactive approach is vital to public safety and disaster preparedness.

Raising public awareness about earthquake preparedness is important. Education programs and drills help communities understand the risks and learn how to respond during an earthquake.

Mega Simulacro (Mega Drill)

Mexico typically holds an annual earthquake drill, known as the “Mega Simulacro” (Mega Drill), on September 19. This date is significant because it marks the anniversary of the earthquake that struck Mexico City in 1985.

Every year at 11:00, the government conducts a national earthquake drill using public loudspeakers located throughout Mexico City to raise awareness and prepare for seismic events.

Mega Simulacro is a nationwide seismic awareness drill that includes practicing evacuation procedures, testing communication systems, and participating in other activities to increase earthquake preparedness.

Frequency of earthquakes in Mexico: A guide for seismic awareness

admin — Sun, 05 Feb 2023 13:57:52 +0000

Mexico is one of the most seismically active countries in the world.

Mexico is located on the Pacific Ring of Fire, an area prone to high levels of seismic activity. This region is known for its tectonic plate boundaries, where the Earth’s plates collide and grind against each other, resulting in earthquakes.

The Pacific Ring of Fire is a region that encompasses the western coasts of North and South America. In this region, three of the world’s largest tectonic plates interact with each other, leading to frequent earthquakes and volcanic eruptions.

Mexico is located on the boundary of two tectonic plates: the North American Plate and the Pacific Plate. The movement of these two plates creates a lot of stress and pressure, which can lead to earthquakes.

Additionally, Mexico has several active seismic zones within its borders, including the Mexican Volcanic Belt and the Gulf of California, both of which are known for high levels of seismic activity.

Earthquakes in Mexico are frequent because of the proximity to the Pacific Ring of Fire, which is a region that is prone to high levels of seismic activity due to tectonic plate interactions.

That’s why it’s important for Mexican residents and travelers to understand the frequency and potential danger of earthquakes so they can be prepared and stay safe.

The Pacific Ring of Fire: The world’s most active seismic zone

The Pacific Ring of Fire is a region that encircles the Pacific Ocean and is known for its frequent and powerful earthquakes and volcanic eruptions. This region is home to over 450 volcanoes and is responsible for approximately 90% of the world’s earthquakes.

The Pacific Ring of Fire is a unique and dynamic region that is both awe-inspiring and dangerous. While it is important to be aware of the potential risks associated with this region, it is also a source of beauty, adventure, and economic opportunity.

Mexico’s connection to the Pacific Ring of Fire

Mexico is located on the Pacific Ring of Fire, a region known for its frequent earthquakes and volcanic eruptions. This dynamic and seismically active region is responsible for the majority of the world’s earthquakes and has significant impacts on countries like Mexico.

Mexico is particularly vulnerable to earthquakes due to its location on the boundary between 2 tectonic plates: the North American Plate and the Cocos Plate. This boundary is known as the Middle America Trench and it is one of the most active seismic zones in the world.

Earthquakes in Mexico can range from small, barely noticeable tremors to catastrophic events that cause widespread damage and loss of life.

One of the most notable examples of the impact of earthquakes in Mexico is the devastating 8.1 magnitude earthquake that struck Mexico City in 1985. This earthquake resulted in the loss of thousands of lives and caused widespread damage to buildings and infrastructure.

Since then, Mexico has implemented a number of important measures to reduce the impact of future earthquakes, including building codes and earthquake-resistant structures.

The Pacific Ring of Fire is not only a source of earthquakes in Mexico, but it is also a source of potential benefits.

For example, the geothermal energy produced by volcanic activity in the Pacific Ring of Fire can be harnessed to produce clean and renewable energy. Additionally, the mineral resources found in the region, such as copper and gold, can support economic growth and development.

The Pacific Ring of Fire is an important and dynamic region that has a significant impact on Mexico and other countries in the region. While earthquakes can be devastating, it is important to recognize the potential benefits of this region, such as geothermal energy and mineral resources.

Whether you are a scientist, a policy maker, or simply a concerned citizen, understanding the impact of the Pacific Ring of Fire is essential for building a safer and more sustainable future.

What to do during a seismic alarm

Mexico is located on the Pacific Ring of Fire, a region known for its frequent earthquakes. Although earthquakes can be unpredictable and frightening, there are steps you can take to stay safe during an earthquake alert in Mexico.

Here are some tips for what to do during an earthquake alert in Mexico:

Drop, cover, and hold on: If you are inside the building and feel the ground shaking, immediately drop to the ground, take cover under a sturdy piece of furniture, and hold on until the shaking stops.

Stay away from windows: Glass windows and other glass objects can break and cause injury during an earthquake, so move away from windows and glass doors and seek shelter in an interior room.

Evacuate tall buildings: If you are in a tall building, evacuate immediately and move to an open space away from buildings, power lines, and other hazards to avoid getting injured from falling objects.

Avoid using elevators: Elevators can become stuck during an earthquake, so it is important to use the stairs to evacuate a building.

Stay tuned to local news: During an earthquake, it is important to stay calm and informed about the actual situation and follow any evacuation orders or emergency instructions issued by local authorities.

Have an earthquake emergency plan: Prepare a detailed plan with your family or coworkers for what to do during an earthquake. This can include designated meeting places and evacuation routes.

Prepare an emergency kit with essentials like food, water, first-aid supplies, and important documents.

Earthquakes in Mexico can be unpredictable and frightening, but by following these tips and being prepared, you can increase your chances of staying safe during an earthquake alert in Mexico.

Stay informed and follow the advice of local authorities to ensure your safety during an earthquake.

2022 Michoacan earthquake

admin — Fri, 23 Sep 2022 06:46:13 +0000

A magnitude 7.6 earthquake struck Mexico on the exact anniversary of 2 devastating earthquakes in 1985 and 2017. The earthquake struck shortly after 13:00 (18:00 GMT) near the Michoacan border with Colima state.

The earthquake was relatively shallow, only 15 km deep, which could have increased its impact. A tsunami warning was issued for coastal areas, saying waves reaching heights of 1 to 3 meters above high tide were possible.

There were no immediate reports of major damage in Mexico City after the quake, which struck Mexico on the same day as devastating earthquakes that previously hit the capital city of Mexico in 1985 and then in 2017.

The National Autonomous University of Mexico (UNAM) said there was no scientific explanation for the three major earthquakes (1985, 2017, and 2022) that occurred on the same day and attributed it to pure coincidence.

The seismic alarm sounded almost 2 minutes prior to the earthquake, allowing residents to evacuate.

Occasionally, the earthquake on September 19, occurred on the same day when Mexico commemorated the devastating 1985 and 2017 earthquakes which killed about 9,500 and 350 people in Mexico City, respectively.

Michoacan earthquake aftershock

A new and powerful earthquake with a preliminary magnitude of 6.8 occurred in Mexico early morning of September 22. The quake comes just three days after a magnitude 7.6 earthquake struck western and central Mexico.

The earthquake, like Monday’s, occurred in the western state of Michoacan near the Pacific coast. The epicenter was located about 46 km south-southwest of Aguilla, in the Michoacan state, at a depth of about 24 km.

The earthquake was felt throughout the state. Damage to a building was reported in the city of Uruapan and several landslides were reported on the highway connecting Michoacán and Guerrero to the coast.

This aftershock from Monday’s earthquake was felt in Colima, Jalisco, and Guerrero.

Seismic activity in Mexico

Due to its location in a seismic zone, Mexico is considered one of the most seismically active countries in the world. Read more about how often earthquakes occur in Mexico and what to do during a seismic alert.

2003 Colima earthquake

admin — Sun, 15 Oct 2017 18:11:58 +0000

The 2003 Colima earthquake occurred on 21 January with a moment magnitude of 7.5 and 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 away as Mexico City and in southern parts of the United States.

Effects

The 2003 Colima earthquake resulted in the death of 29 people and 300 injured. Additionally, approximately 10,000 were left homeless as the earthquake destroyed 2,005 homes and seriously damaged 6,615.

Most of the deaths and damage occurred in Villa de Álvarez, a city that borders the northern part of the city of Colima. Extensive damage (rating VIII) occurred in the city of Colima and in Tecomán.

Some deaths and damage occurred in the states of Jalisco and Michoacán and a few buildings were damaged as far away as Guanajuato and Morelos. The quake was felt strongly (rating VI) in parts of Mexico City.

It was also felt in most of Mexico and in the United States in Corpus Christi, Texas, Dallas, Texas, and El Paso, Texas. Occupants of high-rise buildings in Houston, Texas also reported feeling its effects. Landslides closed a segment of the Colima-Guadalajara Highway and the port of Manzanillo.

Power and telephone outages occurred in Mexico City. A local tsunami of about 1 m (peak-to-trough) was recorded at Manzanillo. A seiche was observed on Lake Pontchartrain in the US state of Louisiana, and sediment was stirred up in several Louisiana wells.

Tectonic summary

This shallow earthquake occurred in a seismically active zone near the coast of central Mexico. The earthquake occurred near the juncture of three tectonic plates: the North American Plate to the northeast, the Rivera Plate to the northwest, and the Cocos Plate to the south.

Both the Rivera Plate and the Cocos Plate are being subsumed beneath the North American Plate.

The slower subducting Rivera Plate is moving northwest at about 2 cm per year relative to the North American Plate and the faster Cocos plate is moving in a similar direction at a rate of about 4.5 cm per year.

Several significant earthquakes have occurred near the recent event.

In 1932, a magnitude 8.4 thrust earthquake struck about 100 km to the north-northwest. On 9 October 1995, a magnitude 7.6 earthquake struck about 50 km to the northwest killing at least 49 people and leaving 1,000 homeless.

The most deadly earthquake in the region occurred about 170 km to the southeast on 19 September 1985. This magnitude 8.0 earthquake killed at least 9,500 people, injured about 30,000, and left 100,000 people homeless.

2017 Chiapas earthquake

admin — Sat, 14 Oct 2017 23:58:22 +0000

The 2017 Chiapas earthquake struck at 23:49 CDT on 7 September (04:49 on the 8th UTC) in the Gulf of Tehuantepec off the southern coast of Mexico, near the state of Chiapas, approximately 87 kilometers south of Pijijiapan.

The magnitude was estimated to be Mw 8.1.

The earthquake caused some buildings in Mexico City to tremble, prompting people to evacuate. It also generated a tsunami with waves of 1.75 meters above tide level, and tsunami alerts were issued for surrounding areas.

Mexico’s president called it the strongest earthquake recorded in the country, in a century. It was also the second strongest recorded in the country’s history, behind the magnitude 8.6 earthquake in 1787, and the most intense recorded globally, so far in 2017.

Tectonic setting

The Gulf of Tehuantepec lies above the convergent boundary where the Cocos Plate is being subducted below the North American Plate at a rate of 6.4 cm/yr (2.5 in/yr).

Background

On 6 September, several earthquake alarms in Mexico City were mistakenly activated and prompted the evacuation of buildings. The incident prompted a review of the system.

Earthquake

According to the National Seismological Service (SSN) of Mexico, the epicenter was located in the Gulf of Tehuantepec, about 137 km southeast of Tonalá, Chiapas. The USA Geological Survey (USGS) reported that the epicenter was about 87 kilometers southwest of Pijijiapan, Chiapas.

The SSN reported a measurement of M 8.2, while the USGS reported an M 8.1 earthquake after correcting an earlier estimate of M 8.0. The earthquake moved the fault between the Cocos and North American plates by up to 10 meters.

The earthquake is the most powerful to be measured in Mexico since the 1985 Mexico City earthquake and is comparable to the 1932 Jalisco earthquake. Mexican President Enrique Peña Nieto called the earthquake the “largest in at least a century” and claimed that it was felt by 50 million people.

Geophysicists at the National Autonomous University of Mexico speculated that the earthquake relieved stored pressure in the “Tehuantepec gap”, making future earthquakes in the region less likely.

Tsunami

A tsunami with waves of 1 m and higher was generated by the earthquake and was recorded at Salina Cruz. A tsunami wave of 1.75 m was reported in Chiapas. The Pacific Tsunami Warning Center issued a warning for the entire Pacific coast of Central America, also extending south to Ecuador.

Aftershocks

In the hour following the earthquake, at least 12 aftershocks were recorded by the USGS. As of 00:30 September 14 (UTC Time), the National Seismological Service (SSN) has recorded at least 1,806 aftershocks, of up to a magnitude of 6.1.

Damage and aftermath

Within Chiapas, an estimated 1.5 million people were affected by the earthquake, with 41,000 homes damaged. Jose Calzada, Minister of Agriculture, reported that at least 98 people had died in the earthquake, including 78 in Oaxaca, 16 in Chiapas, and 4 in Tabasco.

The Secretariat of the Interior declared a state of emergency for 122 municipalities in Chiapas, and the Mexican Army was deployed to aid in disaster relief. Schools were closed on 8 September in 11 states for safety inspections.

Damage in Veracruz was reported, meanwhile, the state is expecting the arrival of Hurricane Katia on 9 September. Hurricane Max made landfall in Guerrero state on 14 September, near the earthquake-stricken region.

Buildings in Juchitán de Zaragoza, Oaxaca, closest to the epicenter, were “reduced to rubble” according to reports from the town’s mayor.

The earthquake also caused buildings to shake and sway in Mexico City, while also knocking out electricity for 1.8 million people.

There were reports of glass shattered at Mexico City International Airport. An under-construction highway bridge near Mexico City’s new international airport collapsed due to the shaking.

The epicenter was near Mexico’s border with Guatemala, where the quake was felt in Guatemala City, and infrastructure damage was reported by CONRED in the nation’s southwest. President Jimmy Morales stated that one Guatemalan may have been killed.

2017 Central Mexico earthquake

admin — Thu, 28 Sep 2017 15:26:50 +0000

The 2017 Central Mexico earthquake struck at 13:14 on 19 September 2017 with a magnitude estimated to be Mw 7.1 and strong shaking for about 20 seconds. It was an epicenter approximately 55 km south of the city of Puebla.

This strong earthquake caused great damage to several central states of Mexico. More than forty buildings collapsed in the states of Puebla, Morelos, and the Greater Mexico City area.

Although Mexico’s SASMEX earthquake warning system provided 20 seconds of advance warning in Mexico City, 342 people were reported killed throughout the region, and more than 6,000 were injured.

The quake occurred on the 32nd anniversary of the 1985 Mexico City earthquake that killed more than 9,500 people. The 1985 quake was commemorated, and a national earthquake drill was held at 11:00, just two hours before the 2017 earthquake.

There had been an even larger earthquake 650 km away off the coast of the state of Chiapas twelve days earlier.

Background

Mexico is one of the most seismically active regions in the world.

Mexico is sitting on top of several intersecting tectonic plates. The border between the Cocos Plate and the North American Plate along the Pacific coast of Mexico creates a subduction zone capable of generating large seismic events.

Taken together with the activity along the edges of the Rivera and Caribbean plates, this causes the country to experience an average of 40 earthquakes a day.

Mexico City is built on a dry lakebed with soft soil made up of sand and clay that amplifies the destruction caused by a major earthquake.

Loose sediments near the surface have a decelerating effect on seismic shockwaves that are slowing them down from 1.5 miles per second to roughly 150 feet per second.

This leads the waves’ amplitude to increase, while deeper and denser soil layers cause shockwaves to endure in the valley longer, thereby extending the length of the earthquake.

Less than two weeks before the Puebla earthquake, Mexico had been struck by an earthquake in Chiapas on 7 September, which killed almost 100 people. Despite its close timing, the Puebla earthquake was not an aftershock of the Chiapas event, as the epicenters were 650 km apart.

The possibility of a link between the earthquakes was investigated in the days after the second one. Big earthquakes can increase the long-term risk of seismic activity by transferring “static stress” to adjacent faults, but only at a distance of up to four times the length of the original rupture.

On 19 September 2017, earthquake static stress transfer was considered unlikely due to the distance between the earthquakes, in excess of the expected 400 km maximum.

“Dynamic triggering”, with seismic waves propagating from one quake affecting other faults, may operate at much longer distances, but usually happens within hours or a few days of the triggering quake; a 12-day gap is hard to explain.

19 September is designated as a day of remembrance for the 1985 Mexico City earthquake, which killed approximately 10,000 residents.

Every year at 11:00, a national earthquake drill is conducted by the government through the use of public loudspeakers located throughout Mexico City. The 2017 drill took place as scheduled, at 11:00, around 2 hours before the new earthquake.

Earthquake

According to the National Seismological Service (SSN) of Mexico, the epicenter was located 12 km southeast of Axochiapan, Morelos, and 120 km from Mexico City. The earthquake was measured at a magnitude of 7.1, occurring at 13:14:40 Central Daylight Time, at a depth of 51 km.

The United States Geological Survey (USGS) placed the epicenter 5 km (3.1 mi) ENE of San Juan Raboso and reported a measurement of VIII (Severe) on the Mercalli intensity scale.

While there was a report of strong shaking for about one minute, which is a long time for an earthquake, acceleration/velocity/displacement seismograms at UNAM showed about 20 seconds of strong shaking with a period of ≈1 second.

SSN reported a peak ground acceleration of 112 cm/s2 (0.114 g0) at the Popocatépetl reporting station in Tlamacas, Estado de México. According to the USGS, the earthquake occurred on a moderately dipping normal fault.

According to the bulletin of Mexico’s SASMEX earthquake warning system, a 20-second advance warning was given in Mexico City.

However, the general experience in the capital was that the alarm and cellphone alerts started only a few seconds before, or during the quake, although some people may have mistaken the alert for a continuation of the earlier drill.

25 of the early-warning seismic sensors detected the earthquake, and alerts were also provided to Oaxaca, Acapulco, Chilpancingo, and Puebla, with lead times stated to range from 12 to 48 seconds.

Casualties

Nine days after the earthquake, at least 333 people had been reported killed. At least 74 people were killed in the state of Morelos, 86 in Mexico City, 45 in Puebla, 13 in the State of Mexico, 6 in the state of Guerrero, and 1 in the state of Oaxaca.

In Mexico City, the bodies of 26 students and four instructors were pulled from the rubble of the Enrique C. Rébsamen school; 30 students and 8 adults were still unaccounted for as of the evening of 19 September.

The Mexico City campus of the Monterrey Institute of Technology and Higher Education suffered damage, with at least 5 people killed and 40 injured.

More than 5.400 people had been reported injured by the day after the earthquake, with more than 295 confirmed dead as Mexico earthquake rescue efforts continue.

On September 26, the death toll climbed to 331, with more than 4500 injured people.

Damage and aftermath

In Puebla, church steeples had toppled in the city of Cholula, and a church on the slopes of Popocatépetl in Atzitzihuacan collapsed during mass, killing 15 people. A second church, which was built in the 17th century, fell in Atzala during a baptism, killing 11 people including the baby.

At least 44 buildings collapsed in Mexico City due to the earthquake, trapping people inside, creating large plumes of dust, and starting fires. At least 50 to 60 people were rescued by emergency workers and citizens.

Several buildings caught fire. Condesa, Roma, and del Valle neighborhoods were among those most affected in the zone: a building located on Álvaro Obregón Avenue collapsed, and several buildings on Ámsterdam Avenue suffered damage.

Gas leaks were reported, along with “piles” of rubble from collapsed buildings. Stock prices declined at the Mexico Stock Exchange but recovered before trading was suspended.

Comisión Federal de Electricidad, the national electric utility, reported that 4.78 million customers lost power in Guerrero, Morelos, Puebla, State of Mexico, Oaxaca, Tlaxcala, and parts of Mexico City—roughly 35% of the company’s customers in those states.

However, none of the generating stations in the region sustained structural damage.

Mexico City International Airport suspended operations while damage assessments took place, but reopened at 4:00 p.m. CDT (2100 UTC). 180 flights were canceled or diverted during the closure. A plane carrying President Enrique Peña Nieto, returning from touring the damage in Oaxaca from the earlier Chiapas earthquake, was diverted to Santa Lucía Air Force Base.

Mexico City Metro service was temporarily canceled on several subway lines due to a power failure, but restored by 17:30, offering free service to stranded passengers. Building evacuations also caused delays to Metrobús’ service in the city.

The federal Secretariat of the Interior (SEGOB) declared a state of emergency for all 33 municipalities of Morelos, all 16 boroughs of Mexico City, and 112 of the 217 municipalities of Puebla.

The declarations allow funds from the National Natural Disaster Fund (FONDEN) to be used during the emergency response phase.

The Mexican Army and Mexican Navy deployed 3,000 active-duty troops to Mexico City through the DN-III-E and Plan Marina emergency response plans. The troops were tasked with debris cleanup, search and rescue, and security missions.

Additionally, the Secretariat of National Defence moved eight helicopters to Mexico City and activated 3 shelters in the affected areas.