Earthquakes in Mexico City: alerts and what to do

Mexico City shakes. You'll probably hear the alert within months of moving. A few minutes of prep now makes those seconds count.

The short version

The seismic alert (alerta sísmica) is run by SASMEX, operated by the nonprofit CIRES. It detects strong quakes near the coast and warns cities before the shaking arrives [1][2].
You'll hear it from nearly 14,000 street loudspeakers run by the city's C5 command center, and on compatible cell phones, radio and TV [3].
The warning can be tens of seconds, or nothing at all. Quakes close to the city can arrive with the alert or before it [1][2].
Mexico City holds national drills, including one every September 19, the anniversary of the 1985 and 2017 quakes [4][5].
Check your building before you sign a lease, and keep a go-bag by the door.

Why Mexico City shakes the way it does

Much of central Mexico City sits on the soft clay of an old lakebed. Seismic waves from quakes hundreds of miles away on the Pacific coast slow down and amplify in that clay, so a distant quake can rattle the city hard. That's why the 1985 quake, magnitude 8.1, was so deadly here even though its epicenter was far away, and why the magnitude 7.1 quake of September 19, 2017, which struck closer, caused so much damage too [5].

What it means for you: the ground under your building matters as much as the building. Neighborhoods on the old lakebed, including parts of Roma, Condesa, the Centro and Del Valle, tend to shake more than hillier areas on firmer ground in the west and south. That doesn't make them off-limits. It makes the building's quality more important.

How the alert works

SASMEX and the speakers

The Mexican Seismic Alert System (SASMEX) is run by the Centro de Instrumentación y Registro Sísmico (CIRES) [1]. Its network of 96 sensors sits mostly along the Pacific coast [2]. When sensors detect a strong quake, the system estimates its size, and if it passes the threshold for a city, a radio signal sets off the alert there [2]. Mexico's national disaster prevention center (CENAPRED) doesn't run any earthquake alert itself [2].

In Mexico City, the alert plays through 13,998 C5 loudspeakers mounted on poles across the city [3]. It's a rising siren with a voice saying "alerta sísmica," and once you've heard it, you won't forget it.

On your phone

During the May 2026 national drill, the alert was also sent to cell phones, radio and TV [3]. For the September 2026 drill, compatible phones got an alert with a distinctive sound and a message saying it was a drill [4]. Make sure emergency alerts are switched on in your phone settings, including if you're on a US carrier roaming in Mexico.

Private alert apps exist too. They can be handy, but they aren't the official system and may sound at a different time.

Why it sometimes doesn't sound

The quake is too small by the system's first estimate, so no alert goes out [2].
The quake is far away and weakens before reaching the city [2].
The quake is close. If the epicenter is near the city, there may not be enough time to warn before the shaking starts [1][2].
The quake is outside the sensor network [1].

So treat the alert as a bonus. If the floor starts moving and there's no siren, act anyway.

What to do when it shakes

The siren gives you somewhere between a few seconds and roughly a minute. Have a plan before you need it.

Stay calm. Don't run, shout or push [5].
If you're on the ground floor or can reach a pre-planned exit in seconds, go to an open area away from buildings, trees and power lines [5]. Many Mexico City buildings drill a quick evacuation, and you'll see neighbors gather in the street.
If you're upstairs, don't run for the stairs or the elevator. Drop, cover and hold on: get down, cover your head and neck, and hold onto sturdy furniture [6].
Stay away from windows, shelves and anything that can fall. Don't stand in a doorway [6].
In bed? Stay there and cover your head with a pillow [6].
Driving? Pull over away from buildings, overpasses and power lines and stay in the car [6].
After the shaking stops, check for gas leaks, take your go-bag and leave calmly by the stairs if the building looks damaged. Expect aftershocks.

The "evacuate or shelter" choice is a real one here, and local guidance leans toward evacuating when you can do it safely in the warning time. Talk it through with your building's administrator and agree on a meeting point.

Checking a building before you rent

This is where you have the most control. Ask questions and look around before you sign.

Check	What to look for
Year built	Mexico City toughened its building code after 1985 and again after 2017. Newer isn't automatically safer, but ask
Damage history	Ask directly whether the building was damaged in 2017 and what repairs were done. Neighbors often know
Visible cracks	Diagonal cracks in walls, especially around windows and doors, and cracked columns are red flags
Ground floor	Buildings with open parking or shops and few walls on the ground floor did poorly in past quakes
Lean	A building that visibly tilts, or doors that won't close, deserves a hard pass
Exits	Two exit routes, clear stairways and no locked gates you can't open fast
Gas	Stationary gas tanks on the roof should be secured; know where the shutoff is
Paperwork	Ask whether there's a structural review on file and a civil protection plan for the building

Heads-up: American renters are used to inspections being someone else's job. Here, a respectful "¿El edificio tuvo daños en 2017?" is a normal question, and a landlord who dodges it is telling you something.

Drills

Mexico City holds national drills (simulacros) a few times a year. In 2026, the first ran on Wednesday, May 6, at 11:00 a.m., based on a magnitude 8.2 scenario off the Guerrero coast [3]. The second ran on Saturday, September 19, at noon, based on a magnitude 7.7 scenario in Tehuacán, Puebla, and commemorated the 1985 and 2017 quakes [4].

Take part. Walk your exit route, time it, and see where your neighbors gather. Kids in Mexico City schools drill regularly, so ask what your school's plan is.

Your emergency kit

Ready.gov's advice works here too: enough food and water for at least three days, a flashlight, a whistle, extra batteries and chargers, and anything specific to your family, like medication and pet supplies [6]. For Mexico City, add:

Copies of your passport and resident card, plus your US documents, in a zip bag. Keep scans in the cloud too.
Cash in pesos. ATMs and card readers may be down.
Sturdy shoes and a jacket next to your bed. Glass breaks, and winter nights at 2,240 m (7,350 feet) get chilly when you're standing in the street at 3 a.m.
A paper list of phone numbers, including family back home and the US Embassy's emergency line for US citizens, +52-55-2579-2000 [7].
Dust masks and work gloves.

Hang a go-bag by the door, not in a back closet.

After a big quake: the US side

Let family know you're OK. Text, don't call; networks jam.
Enroll in STEP before anything happens, so the US Embassy can reach you with alerts and, in a major disaster, check on US citizens.
Lost your passport in the chaos? The embassy can issue an emergency passport.
Renter's insurance for your belongings is worth a look; standard Mexican policies may treat earthquake cover as an add-on, so read the fine print.

Want to know which buildings in your colonia came through 2017 well? Ask the people who live there, and ask in our community group for Americans in Mexico.

Earthquakes in Mexico City: the alert, your building and what to do when it shakes