Amidst the rubble of broken door frames, shards of windows, and concrete pillars in Gaziantep, a Turkish city known for its Byzantine citadels and castles, social media users shared photos of one building in particular that stood firm last month. The surviving structure that made the social media rounds is a stout office, which despite two successive earthquakes that measured 7.8 and 7.7 on the Richter scale, appeared to not even have shattered glass.
The building was designed by the Union of Chambers of Turkish Engineers and Architects, who had for years warned the national government and local officials that earthquakes do not kill people, but poorly constructed buildings do. Their warnings turned out to be prescient. The February 6 earthquake and its aftershocks caused the collapse or severe damage of more than 160,000 buildings in Turkey and Syria. And many of those buildings were apartments, where a large part of the population lives, leading to the deaths of more than 40,000 people.
The destruction of some buildings but not others has drawn attention to the importance of earthquake-safe architecture and building codes in the two countries. Popular Science spoke with structural engineers who study how buildings can withstand earthquakes to understand what makes certain designs more life-saving.
How to engineer buildings for earthquakes
The most important factor when constructing a building that can withstand an earthquake is to make it strong and deformable, meaning that it’s both sturdy but can also bend and sway with the ground without collapsing, says Mehrdad Sasani, an engineering professor at Northeastern University in Massachusetts, who researches earthquake-resilience modeling for buildings.
On a granular level, this means that buildings built from concrete, stone, brick, and similar materials need reinforcing steel bars to make them strong. And to make buildings deformable, engineers need to carefully design and construct the building’s beams and columns, and place the steel bars in a particular way. This strategy is called seismic detailing, and it focuses on areas where the building would experience more impact from severe tremors. The metal rods have multiple joints to help to stabilize the columns, but also allow them to sway and absorb pressure. In finished construction, the metal rods disappear inside the columns and beams, usually behind an apartment’s walls.
Before engineers construct the columns and add the stabilizers, though, they must consider a number of factors, including the ground beneath the building itself. They design buildings based on how severely the earth might shake, rather than a certain magnitude or the earthquake’s number on the Richter scale. “The more severely the ground shakes, the more damaging it’s going to be. That is not directly related to magnitude, but magnitude certainly affects it,” Sasani says.
“The point is this, when the ground starts to shake, buildings start to move. And if that movement is more than the buildings can tolerate, they could collapse. And that shaking is what we design for.”
When building codes save lives
Engineering is only half of the challenge with making dwellings safer during earthquakes. A large reason why the Gaziantep earthquake was so deadly was likely that some developers didn’t follow Turkey’s building codes, which Sasani says are adequate. Three apartment buildings completed in 2019 that were reviewed by the BBC, presumably up to Turkish codes, still collapsed during the disaster. And up to 75,000 buildings in southern Turkey were given construction amnesties, where property owners could pay a fee to be forgiven for construction violations according to Pelin Pınar Giritlioğlu, Istanbul head of the Union of Chambers of Turkish Engineers.
“We cannot design buildings to be earthquake-proof. We make them earthquake-resistant. Even if you follow the standards and codes, there is always a probability of failure and collapse, but that probability is a low probability,” Sasani says. “If buildings were designed based on the code, would some of them collapse? Yes. Would this many [buildings] have collapsed in Turkey and Syria? The answer is no.”
Syria first included earthquake safety measures in its building codes in 1995, and updated them again in 2013. But the country is in the midst of a 12-year civil war, and bombing from the Assad regime likely made structures more vulnerable to collapse during the earthquake, says Bilal Hamad, an engineering professor at the American University of Beirut and a former mayor of Beirut. As a comparison, some of his students studied how the 2020 Port of Beirut explosion, where large quantities of ammonium nitrate that had been idling for several years in the port suddenly combusted, compared to the power of an earthquake.
“Shelling is applying a blast on a building. It’s energy,” Hamad says. “They found similarities, because the [chemical] blast is almost like an earthquake. It is worse even, because the earthquake energy blast is underground. It gets dampened by the soil. But the [chemical] blast is above ground level, and there is nothing that dampens it.”
A way forward for resource-strapped countries
When planning for earthquakes, engineers consider two types of buildings: old and new ones. The way an “old” building is defined is if it was built before engineers applied earthquake science to the most commonly used rules for construction. In the US, Sasani says most codes, which are determined locally, were updated with modern research on seismic forces and construction techniques in the 1970s. Anything built before then is considered an old building.
Sasani says the majority of countries use US building codes, but it takes some time for the rules to travel across land and sea, meaning the date they actually adopted the code could be well past the 1970s. For example, Hamad says that Lebanon didn’t require any earthquake safety in building until 2005. And it took another seven years, until 2012, for the government to require builders to hire technical offices to ensure the buildings were built up to code. In the earthquake’s aftermath, Turkey’s president claimed that 98 percent of the buildings that collapsed were built before 1999, although experts have cast doubt on the statistic, saying it’s been used to divert blame from his construction amnesties policy.
Old structures will therefore probably need rehabilitation, especially if they involve masonry and are built from brick, stone, or other similar material, according to Sasani. Bricks and the like are connected by mortar, which makes them more susceptible to earthquakes, he says. Masonry structures are more common in the global south, where buildings are older, while the US has more structures built from wood, which is less susceptible to earthquake damage.
These older buildings can be rehabilitated through mechanisms such as adding what’s called a shear wall in engineering to make the building stiffer. But rehabilitation is expensive. Sometimes, it’s even cheaper to scrap a building and start a new one. “If you don’t have the resources, you think about your more important priorities,” says Sasani. “If you haven’t had an earthquake in so many decades, you don’t think about that as a priority.” (The last time Turkey and Syria experienced mass casualties from an earthquake was in the 1990s.)
So, what are resource-strapped countries to do? Building inspections aren’t expensive, Sasani says—that’s where they could start. “The least less-developed countries can do is to have codes and standards that are implemented,” he says. “That would reduce the likelihood of events like this in the future.”
It also doesn’t cost very much to make future buildings earthquake safe, explains Karim Najjar, an architecture professor at the American University of Beirut, who researches climate-responsive design strategies. He says adding additional beams and columns to strengthen a building’s infrastructure is usually only a fraction of the total design. “These measures make 5 to 10 percent of the costs for the structures,” Najjar writes in an email to PopSci. “Often cement is reduced in the concrete for maximizing profits,” which can make the building less strong, and therefore, less earthquake-resilient.
Hamad instead estimates the shell of a building costs about 20 percent of the total project. If a building is designed to resist earthquakes, that 20 percent only goes up by 3 to 5 percent. “There would be sheer walls, more reinforcement, beams, columns, and foundations,” he says. “Why not? Safety comes before changing a bathroom.”