They Were Told Their Building Was Earthquake Safe. It Collapsed Anyway.

The upscale three-year-old housing complex of Asur in the Turkish city of Malatya, replete with chandeliers and marble floors, promised to be earthquake safe, built with the best materials to modern seismic codes. Residents in the middle-class neighborhood paid more for those assurances.

One of the compound’s two buildings collapsed in the early hours of Feb. 6, concrete and steel tumbling to the ground in a cloud of dust when a strong aftershock hit the region hours after a 7.8-magnitude earthquake.

It is a pattern that has emerged elsewhere in the earthquake zone: Some structures built to new, strict seismic standards were flattened while others nearby still stood, including older ones that came before the updated rules.

“We didn’t choose our apartment because of the marble bathrooms and beautiful light fixtures,” said Mine Goze, 42, who lives in Block A of the compound with her husband and two children. “We knew we were moving to a high-risk earthquake zone and wanted to be in a safe building, even if it meant paying double the rate of rent in the area.”

Ms. Goze’s husband, who had gone back to their apartment to assess the damage and rescue their cat, managed to get out just before the building collapsed. Most of the residents had already evacuated after the first earthquake.

“It was a close call, many people could have died,” Ms. Goze said. “We demand answers. Why did our building collapse while the other building in our compound remained intact?”

The earthquake and aftershocks that struck southeastern Turkey, killing more than 31,000 people, were strong enough to destroy even buildings that adhered to the codes. But the scope of the devastation, and inconsistent damage to newer buildings, has focused increased scrutiny on the country’s construction regulations and developers’ compliance with the codes aimed at making buildings earthquake safe.

A video of the Asur collapse, analyzed by three engineers with extensive knowledge of buildings and engineering practices in Turkey, found that it was most likely the result of poor structural design. The engineers, who independently assessed the video, all pointed to a flaw known as a weak story.

Each story of a building should have enough lateral strength and stiffness to transfer the load during an earthquake all the way to the ground, said one of the engineers, Mustafa Mahamid, a researcher at Technion-Israel Institute of Technology in Haifa, Israel, and a fellow of the American Society of Civil Engineers. When it doesn’t, he said, the weak story can fail, bringing the building down with it.

“The concrete started collapsing on the ground floor,” said Dr. Mahamid, who has lived and studied in Turkey.

Ihsan Celik, the developer of the residential block that collapsed in the Asur compound, said that the construction of the building was carried out in compliance with the latest regulations, using the highest quality of concrete reinforced with steel bars. He acknowledged that an engineering error may have occurred, causing the collapse of the bottom floor, but said he could not comment further with an ongoing investigation.

“We are still investigating what happened and cannot be sure, but this was a very strong earthquake causing several other new buildings to collapse in the area and people died,” Mr. Celik said. “Thankfully no one died in our building, and we have more than 70 other buildings in the area that are undamaged.”

Across the country, anger is mounting over the lives lost and the millions now without homes and businesses. The Turkish authorities have detained or arrested more than 10 contractors accused of violating building regulations. Several developers were caught trying to flee the country as the Ministry of Justice ordered local officials to set up special units to investigate “earthquake crimes.”

Mr. Celik and his company, Ishak Insaat, have not been implicated in these detentions.

“We draft the laws well, but we do not implement them. This is our biggest problem,” said Pelin Pinar Giritlioglu, the president of the Istanbul branch of the Union of Chambers of Turkish Engineers and Architects.

In 1999, Turkey was hit by a devastating earthquake in the northwestern city of Izmit that killed more than 17,000 people and damaged around 20,000 buildings. Since then, new regulations have been introduced and updated to ensure that structures in fault zones are built to absorb the impact of earthquakes.

But lax enforcement and poor construction practices persist, dogged by concerns about subpar materials and weak inspection protocols. The problems have been exacerbated by a government-backed building boom in recent years that has reshaped city skylines with large residential building projects that are often delivered hastily, without adequate quality control.

The Asur complex is one of many new residential projects built in Malatya, part of the construction frenzy that spurred economic growth across the country. It marketed itself as a “first-class quality” compound, complete with a soccer field and basketball court, attracting families of doctors, police officers and teachers.

Whether the Asur building was drawn up and constructed with potential shortcomings — or whether later modifications weakened it — was not immediately clear. Even for developers committed to following the latest seismic codes, designing a high-rise structure to withstand the lateral forces, shaking and swaying in an earthquake is no simple task.

The three engineers who analyzed the video of the Asur collapse said there appeared to be a design flaw in the ground floor. As the earth shook during the large aftershock, most of the building showed no initial damage, at least as viewed from the outside. Then within seconds dust began spewing from the ground floor — probably pulverized concrete from overwhelmed vertical columns that were beginning to buckle.

It was quickly followed by visible cracking in the external walls on the ground floor as it started collapsing. Finally, that floor all but vanished as the rest of the building — no longer supported from below — crushed it under the force of gravity.

A consulting engineer in Istanbul who analyzed the Asur collapse, Seref Polat, who has worked in the United States and Turkey, said the video showed that the ground floor was the weak story and unable to handle the lateral forces of the earthquake. “It’s a design error,” Dr. Polat said.

That was also the conclusion of Osman E. Ozbulut, an associate professor of civil engineering at the University of Virginia whose hometown in Turkey is about an hour’s drive from Malatya. The bottom story, Dr. Ozbulut said, “seems not to be designed as it should be. It failed and the rest of the building collapsed on top of it.”

All of the engineers said their conclusions were preliminary and could evolve as further information became available from investigations.

In general, the engineers cautioned that an earthquake of this magnitude would do serious damage even in a place like California, where strongly written standards require buildings that are resistant to earthquakes. But many American families live in light, wood-frame houses where a collapse would not necessarily be fatal for those inside, while the more common residences in Turkey are five-to-10 story reinforced concrete apartment buildings that are heavier and more deadly if they come down.

Older buildings in Turkey are more vulnerable. Modern building codes, which started to be adopted in the late 1990s, were revised in 2007 and upgraded in 2018.

An amnesty law introduced in 2018 also undermined efforts to bring buildings up to code. Developers and individuals who violated the country’s building codes could pay a fine to effectively license illegal buildings. The program earned the government $3.1 billion, according to the Ministry of Environment and Urbanization.

Still, many buildings in the earthquake zone should have been built to the newer standards — and some, like the building in Malatya, to the most recent ones, which engineers described as similar to those in the United States. Two buildings collapsed in another brand-new residential complex, Guclu Bahce, in the southern city of Antakya. The complex, which opened with much fanfare in 2019, was marketed as being “particularly special compared to the others in terms of its location and construction qualities.”

Such failures are especially puzzling in a country rich with technical expertise and highly educated engineers. Some engineers said the problems probably had far more to do with a lack of national oversight of design and construction as well as poor practices in the building industry.

Another concern is lax inspection protocols. Under the 2007 building law, structures do not have to be inspected once they have been granted a license, meaning that developers or others can make unauthorized modifications.

“We take our cars to be inspected every two years to ensure that they are safe to drive, but once we construct our buildings and are granted a license, columns can be cut or restorations can be made without consulting an engineer,” said Ms. Giritlioglu from the Union of Chambers of Turkish Engineers and Architects.

Whether it is poor design or inspections, Dr. Mahamid said, even small errors are critical when the earth begins to shake. For example, problems with what engineers call detailing, like subtleties in how vertical columns and horizontal beams are connected, can make the difference between a building that safely sways or collapses in an earthquake.

“I don’t think they follow the detailing that the United States uses in its standards,” Dr. Mahamid said.

Ali Sasmaz, a civil engineer who lives in Block B of the Asur compound, went to inspect the wreckage following the aftershock on Monday. He said the ground floor of the building was commercial with five to six stores and believes it was the weak link.

“I believe the building was sturdy, but it looks like there was a statistical miscalculation in the section where the shops were,” Mr. Sasmaz said.

“Whoever is responsible for the negligence that led to the collapse of this building — the Ministry of Environment and Urbanization, the municipality, the contractor — whoever it is, I want it to be known that we will seek our rights to the end,” he said.

Beril Eski contributed reporting.