The 2017 Central Mexico earthquake struck on 19 September at 13:14 local time with a magnitude of Mw 7.1. The quake lasted about 20 seconds and had its epicenter 55 km south of Puebla, shaking central Mexico and causing destruction in multiple states.

This powerful earthquake severely damaged Puebla, Morelos, and Mexico City, where more than forty buildings collapsed. The event left thousands homeless, triggered fires, and caused structural failures across central Mexico, affecting urban and rural communities alike.

Although the SASMEX early warning system gave Mexico City a 20-second alert, the quake killed 342 people and injured over 6,000. Many survivors recalled confusion because the alarm had just been tested in the annual national drill only two hours earlier.

The quake fell on the 32nd anniversary of the catastrophic 1985 Mexico City earthquake, which killed more than 9,500 people. Ironically, a memorial drill held that morning prepared residents for disaster, but many did not expect another deadly quake so soon.

Just 12 days before, an even stronger earthquake off Chiapas had shaken southern Mexico, killing nearly 100. Although both quakes struck in September 2017, scientists confirmed the Puebla event was not an aftershock, as the epicenters were more than 650 km apart.

Mexico is one of the most seismically active countries, sitting at the junction of several tectonic plates. Along its Pacific coast, the Cocos Plate dives beneath the North American Plate, forming a dangerous subduction zone that regularly produces strong quakes.

Activity is further intensified by movements of the Rivera and Caribbean plates. Together, these interactions cause Mexico to experience an average of 40 measurable earthquakes every day, making it one of the world’s regions most exposed to seismic hazards.

Mexico City is particularly vulnerable. Built on a dried lakebed of clay and sand, the capital’s soft soil amplifies seismic waves. Shaking that would be moderate elsewhere often becomes devastating in the valley, where vibrations resonate and last much longer.

Loose surface sediments slow seismic shockwaves from 1.5 miles per second to about 150 feet per second, increasing their amplitude. The deeper layers then trap the energy, making the ground move more violently and prolonging the destructive shaking in the city.

While the Puebla earthquake struck just days after the Chiapas quake, seismologists explained they were unrelated. Static stress transfer can sometimes trigger nearby faults, but only within about 400 km. The 650 km distance ruled out a direct connection.

Dynamic triggering, where seismic waves from one quake influence another fault, can operate over greater distances. However, this usually occurs within hours or days, not after 12 days, making the Puebla earthquake essentially a separate seismic event.

Each year on 19 September, Mexico commemorates the 1985 Mexico City disaster with a nationwide drill. Sirens sound at 11:00 to remind citizens of earthquake risks. In 2017, this drill took place only two hours before the devastating Puebla earthquake.

Mexico’s National Seismological Service (SSN) located the epicenter 12 km southeast of Axochiapan, Morelos, about 120 km from Mexico City. The quake struck at 13:14:40 CDT with a magnitude of 7.1 and a depth of 51 km, shaking the heart of the country.

The United States Geological Survey (USGS) reported the epicenter near San Juan Raboso, Puebla. On the Mercalli intensity scale, shaking reached VIII (Severe). For many residents, this was among the strongest earthquakes they had ever experienced.

Although some eyewitnesses recalled a minute of shaking, seismographs at UNAM showed about 20 seconds of strong ground motion with a period near one second. Even this short duration was enough to collapse dozens of structures and severely damage many more.

SSN measured peak ground acceleration of 0.114 g at the Popocatépetl station in Tlamacas, Estado de México. USGS analysis indicated the earthquake occurred on a moderately dipping normal fault, typical for crustal quakes within central Mexico.

Mexico’s SASMEX early-warning network issued alerts with varying lead times. In Mexico City, some residents received about 20 seconds to react, while others claimed the alarms sounded only as shaking began. Confusion was worsened by the earlier drill.

In total, 25 seismic sensors detected the earthquake and transmitted alerts to cities including Oaxaca, Acapulco, Chilpancingo, and Puebla. Lead times ranged from 12 to 48 seconds, depending on location, saving lives by giving some residents time to evacuate.

Nine days after the quake, at least 333 deaths were confirmed. Among them, 74 were in Morelos, 86 in Mexico City, 45 in Puebla, 13 in the State of Mexico, 6 in Guerrero, and 1 in Oaxaca. Rescue efforts continued for weeks as more bodies were recovered.

Tragedy struck the Enrique C. Rébsamen school in Mexico City, where 26 students and four instructors died when the building collapsed. Thirty others were initially unaccounted for, highlighting the vulnerability of many schools and public buildings.

The Mexico City campus of Tecnológico de Monterrey also suffered severe damage. Five people were killed, and more than 40 were injured when parts of the prestigious university’s buildings gave way, shocking the academic community nationwide.

By the day after the quake, more than 5,400 people were injured across central Mexico. Rescue teams pulled survivors from the rubble, but as days passed, hopes faded. On 26 September, the official death toll rose to 331, with over 4,500 reported injured.

In Puebla, centuries-old churches were among the worst-hit. A church in Atzitzihuacan collapsed during mass, killing 15. Another, built in the 17th century in Atzala, fell during a baptism, tragically killing 11 people, including the baby and family members.

In Mexico City, at least 44 buildings collapsed, sending clouds of dust into the air and trapping people inside. Condesa, Roma, and del Valle were especially hard hit, with residential towers and offices crumbling in scenes reminiscent of the 1985 disaster.

Emergency workers and volunteers rescued 50 to 60 people from collapsed buildings. Fires erupted, gas leaks spread, and piles of rubble blocked streets. Álvaro Obregón Avenue and Ámsterdam Avenue became symbols of the capital’s devastation and resilience.

Across central Mexico, 4.78 million people lost power, about 35% of customers in affected states. The Comisión Federal de Electricidad confirmed no structural damage to power plants, but widespread outages paralyzed daily life and emergency operations.

Mexico City International Airport halted operations for safety checks, leading to 180 canceled or diverted flights. A plane carrying President Enrique Peña Nieto was rerouted to Santa Lucía Air Base as he returned from inspecting Chiapas earthquake damage.

The city’s Metro was disrupted as power failures shut down several lines, though service resumed by late afternoon and was made free to help stranded passengers. Metrobús lines were delayed as evacuations and building collapses blocked streets across the city.

The federal government declared emergencies in all 33 municipalities of Morelos, 112 of Puebla’s 217 municipalities, and all 16 boroughs of Mexico City. This triggered access to funds from FONDEN, Mexico’s disaster relief fund, to support emergency response.

The Mexican Army and Navy deployed 3,000 troops under DN-III-E and Plan Marina to clear debris, conduct rescues, and secure collapsed areas. Helicopters provided aerial support, while temporary shelters opened to house displaced families in affected regions.