What is the building code in the Turkish region hit by the recent earthquake?

Question

I saw some pictures of the destruction caused by the earthquake that it the Southern region of Turkey and part of Syria in February 2023. I noticed that some modern building collapsed while other buildings close by remained intact, they seem to be built in the same period. I imagine that the building standards are not very consistent, but was a seismic code mandatory? What are the minimal legal standards in the region?

I am not asking about Syria because I assume that enforcing any legal standard in the region is and was quite difficult.

Answer 1

News is starting to come out that it was less the building codes themselves than their enforcement or lack thereof, sometimes even on new buildings. Technical details about building codes don't really belong here, but enforcement and political will to tackle the problem is on topic.

Stricter safety standards were also brought in following the 1999 earthquake around the city of Izmit, in the north-west of the country, in which 17,000 people died.

The latest rules require structures in earthquake-prone regions to use high quality concrete reinforced with steel bars. Columns and beams must also be distributed to effectively absorb the impact of earthquakes.

These laws, however, have been poorly enforced.

"In part the problem is that there's very little retrofitting of existing buildings, but there's also very little enforcement of building standards on new builds," says Prof Alexander.

...

The recent construction means it should have been built to the latest standards, updated in 2018, which require structures in earthquake-prone regions to use high-quality concrete reinforced with steel bars.

We have seen similar issues in countries with poor governance however. It can sometimes be easier to bribe inspectors than do it right. Turkey's Transparency International corruption rating is iffy and has been trending down. And, similar questions were asked after the 1999 earthquake.

The code was updated at least twice, in 2007/2017 (my local building code also has 10 year update cycles wrt earthquakes as risks are better understood and building engineering progresses):

Turkish experts agree that new buildings’ constructed in compliance with 2007 and 2017 earthquake regulations reduced destruction relatively, but they highlight that the measures taken did not go far enough.

And bribes may not even have necessary either, as the government seems willing to consider compliance avoidance as a profit center.

She explained that as part of the 2018 zoning amnesty, licences were given to buildings built before 2017 which may not have adhered to building codes or zoning, in return for a fee paid to the government. In Turkey, 13 million structures were legalized under this law.

Keep in mind before criticizing overmuch: this earthquake was quite violent. And it is quite costly to retrofit older existing buildings, so saying that it should be done in all cases is unrealistic.

Where I live there used to be quite a long list of complaints about the seismic readiness of schools, but the government has slowly been fixing them. Older rental stock is quite vulnerable, but since housing is in short supply...

Also, not sure about earthquakes, but plenty of post-mortem on forest fires in the NorthWest/California shows that there is plenty of apparently-random variability on outcomes - one house might be left standing amidst a patch of razed identical houses. Don't read too much into isolated pictures.

Last, but not least, earthquakes are hard to compare to each other. We see a headline number - the magnitude. But that is at a point location, where it happens, not necessarily where a city is located. If we take hurricanes, no one is going to say Oh, Hurricane Gabriella was 320 kph at peak (at one location) and look how well Miami withstood it. (fictitious example). They'll speak of winds at Miami.

Kobe, Japan in 1995 had 6.9 and 6000+ deaths IIRC, which might compare badly to Los Angeles, 6.7 in 1994, 50 deaths. But is it fair to say that Japan is 100x less well prepared to earthquakes than California? Few would make that claim and it would take some more work to make meaningful comparisons.

That all said, Turkey's government under Erdogan is not exactly covering itself with glory on disaster response and maybe a comparison to Kobe is warranted, where Japan dithered needlessly (one Japanese military officer had to act on his own initiative to send in his troops, IIRC, when central command wasn't doing anything).

In fact, Reuters reports the same about Turkey:

Nasuh Mahruki, founder of a search and rescue group active in response to the 1999 earthquake that killed 17,000, said the army did not act soon enough because Erdogan's government annulled a protocol enabling it to respond without instruction.

Answer 2

Apparently the construction codes were strict enough and it's enforcement that was the primary issue. According to a recent article (Google Translated and edited):

The earthquakes of magnitude 7.7 and 7.6 in Kahramanmaraş caused destruction in 10 provinces, resulting in thousands of buildings collapsing and thousands of people losing their lives. Despite this, it was discovered that not a single building in the Erzin district of Hatay was destroyed, and no one died due to the destruction. This district is 110 kilometers from Hatay and 20 kilometers from Osmaniye, where the earthquake caused great damage.

The mayor of Erzin, Ökkeş Elmasoğlu, stated that there were no casualties in Erzin due to the earthquake, and that there were no injuries or buildings that were destroyed. He added that while there were 50-60 deaths in Iskenderun, Hatay, and Osmaniye, there were no deaths in Erzin due to the earthquake.

Erzin Mayor Ökkeş Elmasoğlu said that although they were happy for their district, their joy was incomplete due to the deaths caused by the earthquake. He also described his own experience of the earthquake, saying that he and his family were shaken so hard that it was difficult to move and that the earthquake seemed to never end. After the shaking stopped, they left their house with the things they could grab and started walking around the district. He was relieved to find that there was no ruin in Erzin.

Ökkeş Elmasoğlu, the mayor of Erzin, stated that he did not allow any illegal construction in the district during his time, and that he has a clear conscience about it. He also said that even though he could not stop illegal construction completely, he did his best to reduce it, and that he would not tolerate it and would take action if necessary, without mixing politics into it.

The fact that no buildings were destroyed in Erzin district of Hatay during the earthquake reminded people of Tavsancil in Dilovasi district of Kocaeli, which was the only place that was not destroyed in the 17 August 1999 Gölcük earthquake. This was remarkable because the Gulf region was almost completely flattened by the earthquake, yet Tavsancil was not affected due to its zoning plan, even though it was located at the epicenter.

Another source clarifies that Erzin didn't have any high-rise buildings:

The mayor also pointed out that the majority of the houses in the district are either detached or four-story, while the highest number of floors is six, which is very few.

The Erzin district is located 76km from the epicenter. Assuming the article is indeed correct about the lack of collapsed buildings in the district, it seems like lack of enforcement was the main culprit in many cases, at least when it comes to buildings with 6 floors or lower.