This story also appears in Spanish on our sister site, CityLab Latino.

On Tuesday, September 19, Mexico City’s architectural cultural center, in the Condesa neighborhood, was confirming the final reservations for an inauguration that evening of a new exhibit: “Mexico City: 1985 Earthquake.”

The exhibit at La Casa del Arquitecto, the House of the Architect, marked the 32nd anniversary of Mexico’s most devastating earthquake in the past century.

Then, at 1:14 p.m., everything began to sway.

It was a 7.1 magnitude earthquake on the border of the nearby states of Morelos and Puebla. The quake rocked Mexico City in the middle of the workday, and across the metro area, people poured into the streets, panicked.

La Casa del Arquitecto called off the event commemorating the earthquake that decimated the city exactly 32 years before, and went into crisis mode.

Within hours, La Casa became the de facto headquarters for local architects and engineers volunteering to assess damage across the city. El Colegio de Arquitectos, a professional organization also based in Mexico City, launched the brigadacdmx@gmail.com email address on Tuesday afternoon and called for residents to write in with reports of buildings damaged in the earthquake.

Thousands of volunteers were already rushing to the sites of dozens of collapsed buildings across the city. But as emergency phone lines jammed, and police were dispatched to the most catastrophic sites, concerned residents had no way to know if the damage to their homes posed an imminent threat.

Hundreds of emails began flooding the account. Those residents who had made it out of their homes re-entered to see massive cracks on interior walls, shattered windows, and crumbling facades. They all had the same question: Am I going to be safe?

Twenty-four hours after the quake, at La Casa del Arquitecto, architects, engineers, and structural specialists lined up to offer their services. The queue snaked past the new exhibition, featuring photographs of the 1985 quake.

Susana Miranda Ruíz, Vice President of Professional Development of the Colegio de Arquitectos, says that as of noon on Wednesday, they had already received over 1,000 requests for assistance.

“The [architects, engineers, and structural specialists volunteering their services] assess the damage, and when they get back here, we process the information they have collected and follow up if the building needs more specialized attention,” says Ruíz, her cell phone buzzing with notifications every few seconds.

At each site, volunteers go through a detailed checklist, from the characteristics of the foundation to the type of wall material.

Ruíz estimates that 300 volunteers had registered as of late Wednesday afternoon, and will need all week to catch up on the backlog of citizen reports. Volunteers are sent in teams as a safety precaution. Ruíz adds that the President of the Colegio, Féliz Villaseñor Jímenez, is in direct communication with the office of Mexico City mayor Miguel Ángel Mancera.

Carlo Cisneros, a civil engineer in Mexico City, arrived to volunteer on Wednesday. Cisneros explains that a combination of factors make neighborhoods like Condesa, Roma, and Del Valle particularly vulnerable to the impacts of the quake.

Cisneros explains how the building code divides the city into three soil zones: “lake soil,” the least dense, “transitional,” and “bank soil,” the densest. The type of soil dictates how deep the foundation must be for new constructions, among other earthquake precautions.

An earthquake’s energy waves gain more momentum in the lake soil of neighborhoods like Roma and Condesa, resulting in more damage to buildings. Another engineer waiting to volunteer compares the soil here in Condesa to jello.

Cisneros says that corner buildings are also more vulnerable, because they cannot pass the energy of an earthquake on to an adjoining building. This results in a phenomenon called torsion. “The building starts to twist, and there is nothing that will stop it,” says Cisneros.

Another engineer points out that the mix of new and old buildings in neighborhoods like Roma and Condesa can make building collapse more likely. New construction projects follow strict building codes, but their deep foundations can cause the soil to shift and resettle under nearby buildings. When an earthquake strikes, these buildings, often constructed between the 1960s and ‘80s and with thinner walls and more shallow foundations, are among the first to fall.

Once Cisneros is registered at the Casa del Arquitecto, he is dispatched to an apartment building in the Narvarte neighborhood, along with the architect Ángel Saucedo. They drive a half hour through the traffic that had clogged the impacted neighborhoods all day, and park on a quiet block in the residential neighborhood.

Neighbors come out of their homes and ask if the pair can also assess their buildings. The volunteers end up assessing four buildings on the block, none of which have suffered structural damage.

The neighbors are grateful to hear the engineer and architect’s verdicts. An elderly woman who lives alone says she had tried calling Civil Protection but that the line was busy every time. Now she knows that the cracks that appeared on her dining room walls don’t pose an immediate threat.

Driving back to the meeting place, we pass dozens of people standing on sidewalks, with blankets and backpacks in hand. Many have been evacuated from their apartment buildings, and will have to sleep elsewhere.

Reports have come in throughout the day of buildings collapsing, and volunteers struggle to confirm whether the accounts are true. There is no estimate yet of how many buildings will have to be demolished.

Cisneros says that the building code is very specific in what constitutes irreparable damage. The roof caving in can be an obvious sign. In other cases, the angle of fallen beams can be enough to determine whether a building can be saved.

Cisneros lays the blame for the earthquake’s disastrous impacts on the government. He explains it is the city government’s responsibility to send inspectors to assess the earthquake risk for buildings around the city.

However, Cisneros, and Francisco Soriana, another civil engineer who volunteered on Wednesday, agree that some construction companies cut corners and sacrifice safety. Soriana says that sometimes more resilient construction materials are passed up for cheaper alternatives. One example: substituting porous tezontle for the hard gravel that is recommended for building atop “transition” soil.

Since the 1985 earthquake, the Mexico City government created the role of “Director Responsible for Construction” (DRO in Spanish), who is legally responsible for the structural integrity of the building after construction is completed. The Urban Development and Housing Secretariat (Seduvi) can sanction DROs who failed to follow the building code.

Some of these buildings had been declared unsound or uninhabitable before this month’s earthquake, but residents remained there. Now, after the earthquake, many people will need to move out of their homes, but they may try and stay because of a lack of resources to move, or sentimental attachment. “Someone’s home is their patrimony, and even if it is unsafe, some people just don’t want to leave,” Soriana says.

In the weeks and months to come, after the structures have been inspected, many Mexico City residents will face the tough decision of whether to walk away from their homes for good.