Expert explains... Did the 6.2 tremor trigger the major earthquake? He listed the risky districts in Istanbul!

Prof. Dr. Cenk Yaltırak, a member of the Marmara Active Fault Hazard and Risk Application and Research Center (MATAM) Group, made important assessments regarding the 6.2 magnitude earthquake that occurred in Istanbul on April 23.

'NOT DOOMONGERING, BUT A SCIENTIFIC ESTIMATE'

Speaking to Cansu Çamlıbel from T24, Prof. Dr. Cenk Yaltırak stated that in order to understand whether the 6.2 magnitude earthquake affected the expected major earthquake, the aftershocks must first subside. Prof. Dr. Cenk Yaltırak said, "If you say something about this immediately after the earthquake, it is a comment not based on science."

Stating that the expected major earthquake will have a maximum magnitude of 7.8, Prof. Dr. Yaltırak said, "This is a scientific estimate, not doomongering. It won't be any bigger. It won't be much smaller either."

Sharing which districts in Istanbul have the highest and lowest earthquake risk, Prof. Dr. Yaltırak said, "It is wrong to describe the earthquake as if it will hit or destroy every place with the same acceleration. For example, if the houses in Maslak were to collapse, no one in Istanbul would have a chance of survival. There is no fault that could create such an earthquake."

'THE EXPECTED EARTHQUAKE WILL HAVE A MAXIMUM MAGNITUDE OF 7.8'

Stating that the magnitude of the expected earthquake in Istanbul could reach a maximum of 7.8, Prof. Dr. Cenk Yaltırak said, "This is a scientific estimate, not doomongering. It won't be any bigger. It won't be much smaller either. When we read the history of earthquakes, the periodic assumption tells us that the big earthquake has a condition to destroy certain places. Nothing was destroyed in this 6.2 magnitude tremor. For example, there are historical buildings built before 1766, and none of them were destroyed. This means this is not that big earthquake. The one on April 23 is a medium-sized earthquake. There are articles and doctoral theses about how much the historical buildings in Istanbul were destroyed and when. For example, Deniz Mazlum has a very beautiful book about the 1766 repairs. If this fault is creeping, for instance, did it forget to do so and remain locked? There are records in the Marmara region indicating that medium-sized earthquakes, whose locations are not certain, began approximately 10 years before major earthquakes, and their numbers varied between 2 and 8. But these are in a complex pattern. It is not characteristic of every segment," he said.

Regarding whether the 6.2 magnitude earthquake affected the expected major earthquake, he spoke as follows:

-There are many faults branching off from the main faults where we expect the actual earthquake. This 6.2 magnitude Central Marmara Ridge Earthquake occurred on one of these faults. Now there are some faults close to it. The movements on those faults also affect the main fault. But does it affect the general magnitude of the major earthquake we expect? No, it does not.

-From this perspective, we can easily say that the stress on this fault has not been released. I always explain this with a door analogy. The Marmara segments of the North Anatolian Fault consist of doors; as we lean against those doors, the hinges of the doors creak, crack, and pop. But that door also has a lock.

-The lock is the place where we expect the fault to break. When an earthquake occurs on the hinges, a load is also placed on that lock.

-But we cannot say for this situation that "it brought forward or delayed an expected earthquake." It is not possible to say this. Because there is such a thing as magnitude. In other words, when you remove a teaspoon of water from a 20-liter bucket of water, you haven't lost much in terms of volume.

'AFTERSHOCKS MUST END TO UNDERSTAND THE EFFECT ON THE EARTHQUAKE'

The teaspoon is just an analogy. If you calculate the mathematical equivalent of this, the moment drop across the entire main fault would be about Mw 0.03. If it were a 7.37 magnitude earthquake instead of 7.4, this difference would not even be visible in seismic records. To understand whether this earthquake made a negative or positive contribution to a destructive earthquake, these aftershocks must first end. We need to see which area they spread to. We need to look at their total energy. And we need to see how this total energy changes the environment. In other words, there is actually no data to say this the day after the earthquake, technically speaking. If you say this, you are making a comment that is not based on science."

WHICH DISTRICTS HAVE SOLID GROUND?

He stated that districts such as Beykoz, Sarıyer, Beşiktaş, and Şişli have solid ground and that there would not be major destruction if a 7.8 magnitude earthquake were to occur.

Prof. Dr. Cenk Yaltırak stated that Fatih, Zeytinburnu, the shores of the Golden Horn, the valleys of Istanbul, Kağıthane, Kasımpaşa, Büyükçekmece, and Küçükçekmece would be more affected, and that priority should be given to buildings in these districts.

Prof. Dr. Yaltırak said, "My house is around Maslak. If the houses where I am were to collapse, no one in Istanbul would have a chance of survival. There is no fault that could create such an earthquake, or any accumulation or effect that would create this. It is wrong to describe the earthquake as if it will hit or destroy every place with the same acceleration. Even in the worst-case scenario of 7.8, we only see the 0.2g acceleration felt on the coast on April 23 on the solid ground of Istanbul. They go and transform buildings in solid places, and thus national wealth is wasted. Because those buildings have no chance of collapsing. Maybe they will get through it with minor damage. Maybe they will be saved with reinforcement. But what are you doing? You are equipping Beykoz, Sarıyer, Beşiktaş, and Şişli from top to bottom with new buildings. You are both increasing prices and increasing rents. The city is becoming unlivable. The gap between them is increasing," he said.