The 2017 Puebla earthquake, also known as 19S, struck at 13:14 CDT (18:14 UTC) on 19 September 2017 with an estimated magnitude of 7.1 Mw and strong shaking for about 20 seconds. Its epicenter was about 55 km (34 mi) south of the city of Puebla, Mexico. The earthquake caused damage in the Mexican states of Puebla and Morelos and in the Greater Mexico City area, including the collapse of more than 40 buildings. 370 people were killed by the earthquake and related building collapses, including 228 in Mexico City, and more than 6,000 were injured.
The quake coincidentally occurred on the 32nd anniversary of the 1985 Mexico City earthquake, which killed around 10,000 people. The 1985 quake was commemorated, and a national earthquake drill was held, at 11 a.m. local time, just two hours before the 2017 earthquake. Twelve days earlier, the even larger 2017 Chiapas earthquake struck 650 km (400 mi) away, off the coast of the state of Chiapas.
Mexico is one of the world's most seismically active regions, sitting atop several intersecting tectonic plates. The border between the Cocos plate and North American plate, along the Pacific Coast of Mexico, creates a subduction zone that generates large seismic events. Activity along the edges of the Rivera and Caribbean plates also generate seismic events. All together, these seismic forces cause an average of 40 earthquakes a day in Mexico.
Mexico City is built on a dry lakebed with soft soil made up of sand and clay, which amplifies the destruction that major earthquakes cause. Loose sediments near the surface slow the shockwaves' speed from about 2.4 kilometres per second (8,600 km/h; 1.5 mi/s) to roughly 45 metres per second (160 km/h; 150 ft/s). This increases the shockwaves' amplitude, which causes more violent shaking. Deeper and denser soil layers increase amplified shockwaves' destructive duration.
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 (400 mi) apart.
The possibility of a link between the earthquakes was being 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. In the 19 September 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 people. Every year at 11 a.m., 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 a.m., around two hours before the central Mexico earthquake.
According to the National Seismological Service (SSN) of Mexico, the epicenter was located 12 km (7.5 mi) southeast of Axochiapan, Morelos, and 120 km (75 mi) 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 48 km (30 mi). 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. Post-earthquake surveys indicated a maximum intensity of IX (Violent) near the epicenter region. 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, 20 seconds' 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. Some residents reportedly mistook 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.
Nine days after the earthquake, at least 361 people had been reported killed. At least 74 people were killed in the state of Morelos, 220 in Mexico City, 45 in Puebla, 13 in the State of Mexico, 6 in the state of Guerrero and one 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 6,000 people had been reported injured by the day after the earthquake, with more than 300 confirmed dead as rescue efforts continued.
On 1 October the number of people known to have been killed was stated to be 361, with more than 4,500 injured. By place, 220 were killed in Mexico City, 74 in the state of Morelos, 45 in Puebla, 15 in Mexico State, six in Guerrero, and one in Oaxaca.
An investigation published in October 2017 revealed that since 2012 there had been over 6,000 complaints about construction violations in Mexico City, with no public record of how many were followed up. Many of the buildings complained about collapsed in the 19 September earthquake. After the earthquake the Urban Development and Housing Secretariat (Seduvi) did not respond to requests for information on responses to complaints. Local activists called the construction system totally corrupt, and said that some developers circumvent building regulations, and city authorities frequently ignore complaints. Mónica García Villegas, the owner of Colegio Rébsamen in Mexico City where 26 people including 19 children died when the building collapsed, was found guilty on 17 September 2020 of "culpable homicide" for ignoring safety regulations. The Mexico City prosecutor (FGJ-CdMx) asked for 57 years of prison.
The casualties included eight foreigners, including four Taiwanese women, a Korean man, a Spanish man, a Panamanian woman and an Argentine man. The actress Cecilia Suárez was injured while filming The House of Flowers in Condesa, Mexico City. Another famous fatality of the earthquake was Adela Peralta Leppe, Mexico's first female clown. Trapped under rubble for 30 hours after her building collapsed on her, Peralta died months later due to complications.
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 a 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 neighbourhoods were among those most affected in the zone: a building located on Álvaro Obregón Avenue collapsed, and several buildings on Ámsterdam Avenue suffered damage. The building housing the Philippine Embassy in Mexico City was badly damaged, requiring it to vacate the property.