September 19 is a date that feels cursed in Mexico City. Seriously. It’s the kind of coincidence that makes even the most hardened skeptics look at the sky and wonder what’s going on. In 1985, a massive quake leveled parts of the city on that day. Then, exactly 32 years later, it happened again. People had literally just finished the annual commemorative earthquake drill—the sirens had barely stopped ringing in their ears—when the ground started rolling for real.
The Mexico City 2017 earthquake, or the Puebla-Morelos earthquake as scientists usually call it, wasn’t just another tremor. It was a $M_w 7.1$ event that caught everyone off guard because of where it started. Most big Mexican quakes happen way out on the coast, giving the city’s early warning system about a minute to alert people. This time? The epicenter was only about 75 miles away in the state of Puebla. The alarm didn't go off until the shaking had already begun. That lack of a head start changed everything.
The Science of Why Mexico City is a Geologic Nightmare
Basically, the city is built on a bowl of jelly. It's an old lakebed, and when seismic waves hit that soft silt and clay, they don't just pass through. They get amplified. They bounce around.
Think about a bowl of Jell-O. If you tap the side of the bowl, the center jiggles way more than the edges. That's Mexico City. During the Mexico City 2017 earthquake, the ground motion in certain neighborhoods like Roma and Condesa was far more violent than in places built on solid volcanic rock, like the UNAM campus further south. It’s a phenomenon called site amplification, and it’s the reason why a building on one block might collapse while the one next door doesn't have a single crack.
The 2017 event was also an "intraplate" earthquake. This means it happened within the Cocos Plate as it dived beneath the North American Plate, rather than at the actual boundary between them. These types of quakes produce high-frequency shaking that is particularly brutal on shorter buildings, usually those between four and eight stories tall.
What Really Happened in the Streets
It was 1:14 PM. Most people were at work or school. When the shaking started, it wasn't the slow, rhythmic sway people are used to in the capital. It was a violent, vertical jolt.
Dust. That's what people remember most. The sight of gray clouds rising from collapsing concrete.
You've probably heard of the Enrique Rébsamen school. It became the tragic face of the disaster when a wing of the building collapsed, killing 19 children and seven adults. It was a mess of corruption and bad engineering; the owner had built a heavy private apartment on top of the school structure that it was never designed to hold. It’s a grim reminder that "natural" disasters are often heavily influenced by very human mistakes.
Then there was the "Frida Sofía" saga. For hours, the world watched as rescuers claimed to be communicating with a young girl trapped in the rubble of the school. It turned out she didn't exist. It was a weird mix of chaos, exhaustion, and desperate hope that led to a massive communication breakdown between the Navy and the media. Honestly, it was a low point in the reporting of the crisis, but it showed just how much the city was reeling.
The Rise of the Brigadistas
While the government struggled to coordinate, the citizens didn't wait. Thousands of people—mostly young adults—poured into the streets. They formed human chains to move buckets of debris. They used motorcycles to weave through gridlocked traffic to deliver water and bandages. They called themselves "Brigadistas."
- They used the hashtag #Verificado19 to check which buildings actually needed help.
- They marked gas leaks with spray paint.
- They stayed awake for 72 hours straight digging with their bare hands.
It was an incredible display of "solidaridad." If you talk to anyone who lived through it, they’ll tell you the government felt absent, but the neighbors were everywhere.
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Why Some Buildings Fell and Others Stood Still
Engineering isn't just about strength; it's about flexibility. Many of the buildings that went down during the Mexico City 2017 earthquake were built before the 1985 codes were put in place, or they were "soft-story" structures. A soft-story building is one where the ground floor has big open spaces—like a parking garage or a lobby with big windows—and then several floors of heavy apartments above it.
During a quake, that bottom floor can't handle the sideways force (the shear) and it just folds like a house of cards.
Interestingly, many buildings that survived 1985 ended up failing in 2017. Why? Because seismic waves have different "personalities." The 1985 quake had long-period waves that targeted tall skyscrapers. The 2017 quake had short-period waves that were a death sentence for mid-rise, older masonry buildings.
The Corruption Factor
We have to talk about the "cartel inmobiliario" (real estate cartel). Investigations after the quake found that many of the newer apartments that collapsed—some only a few years old—had used substandard materials. In some cases, builders had bribed officials to sign off on plans that skipped crucial steel reinforcements.
For example, in the Portales neighborhood, a brand-new apartment complex collapsed, killing two people. It was later found the building lacked the necessary structural support despite being marketed as "earthquake resistant." It's a reminder that even the best building codes in the world are useless if nobody enforces them.
The Economic and Psychological Hangover
The damage wasn't just physical. The Mexico City 2017 earthquake cost the country billions of pesos. But the psychological cost was arguably higher.
Post-Traumatic Stress Disorder (PTSD) spiked across the city. Even years later, the sound of the seismic alarm—a haunting, low-frequency wail—causes people to have full-blown panic attacks. I’ve seen people sprint out of restaurants because a heavy truck drove by and rattled the windows. That kind of trauma doesn't just go away.
The real estate market shifted, too. Neighborhoods like Roma and Condesa, which are trendy and beautiful but sit on that "jelly" lakebed, saw a temporary dip in prices. People started looking for homes in "zona de piedra"—the rocky areas like San Ángel or Copilco. But, memories are short. Today, those trendy neighborhoods are more expensive than ever, proving that the desire to live in the heart of the culture often outweighs the fear of the next big one.
How to Stay Safe: Lessons from 2017
If you live in or are visiting a seismic zone, there are a few things that the 2017 experience taught us that are actually useful. Don't just ignore this; it's the difference between being a victim and being a survivor.
First, know your soil. If you're in Mexico City, check the seismic maps. Are you on the old lakebed (Zona III) or the transition zone (Zona II)?
Second, the "Triangle of Life" theory—crawling next to a sofa or bed—is mostly debunked for modern concrete buildings. The gold standard is still "Drop, Cover, and Hold On." Get under a sturdy table. If the building starts to pancake, that table is your best shot at a void space.
Third, have a "go-bag" that isn't just a backpack with some old crackers. It needs:
- Copies of your ID and house deeds in a waterproof bag. (Many people lost their homes and couldn't prove they owned the land).
- A portable power bank. In 2017, cellular networks stayed up in some areas, but nobody had a charge.
- A whistle. Rescuers listen for sounds in the rubble. Your voice will give out long before a whistle does.
- Wrench or pliers. To turn off gas lines. Gas fires killed a lot of people after the initial shaking stopped.
Where Do We Go From Here?
The Mexico City 2017 earthquake was a wake-up call that the city's defenses were good, but not perfect. Since then, the early warning system (SASMEX) has been expanded. More sensors have been placed closer to the city.
However, the biggest challenge remains the "informal" housing. Millions of people in the surrounding State of Mexico live in houses they built themselves, brick by brick, without an engineer in sight. These areas are the most vulnerable and the least protected.
The 2017 event showed us that technology is great, but community is what saves lives in the first hour. It also taught us that we can't just prepare for the "last" earthquake. We have to prepare for the one we haven't seen yet.
If you want to be proactive, start by inspecting your own home. Look for "X" shaped cracks in your walls. That’s a sign of structural stress. Look for columns that seem too thin for the roof they're holding. Don't wait for the next September 19 to think about it.
Actionable Steps for Seismic Preparedness
- Download apps like SkyAlert or Sismo Detector. These often provide a few extra seconds of warning by using private sensor networks that complement the official sirens.
- Verify your building's safety certificate. In Mexico City, this is the "Dictamen de Seguridad Estructural." If your landlord doesn't have one, ask why.
- Establish a family meeting point outside of your neighborhood. In 2017, phone lines were jammed for hours. You need to know where to go if you can't call home.
- Practice a "blind" exit. Can you get out of your apartment in total darkness? Smoke and dust will likely blind you during a real event. Feel the walls, count the doors.
The 2017 quake was a tragedy, but it was also a masterclass in human resilience. The city didn't just break; it learned. And in a place where the earth is guaranteed to move again, learning is the only way to survive.