60 percent of the European side and 40 percent of Asia are at risk
Geological engineer Prof. Dr. Haluk Selim, regarding the earthquake, which is one of the most important topics of Istanbul, said: "If we assume that the North Marmara Fault Line, which is about 100 kilometers long, has accumulated a stress of 5 meters, its maximum and minimum range is 7.2 to 7.4. The calculation for this is clear. 40 percent of the Anatolian Side and 60 percent of the European Side are at risk.”
Selim, who also gave examples from the big earthquakes that occurred before, stated that the magnitude of the earthquakes depends on the length and the accumulated stress pulses and continued his words as follows;
“The deceased Aykut Barka started work on historical earthquakes 20 years ago. I was also involved in that study. It gave a 250-year earthquake period. When you look at this 250-year period, after 99 earthquakes, no earthquakes occurred, and this 115-kilometer fracture is still in place as a seismic gap. If it breaks in a possible earthquake, we are talking about a 100-kilometer-long fault for Istanbul, and if you assume that it has accumulated a stress pulse of 5 meters, the maximum and minimum range is 7.2 to 7.4, and there are examples. Remember the Gölcük Earthquake, if you remember the East Marmara Izmit Earthquake, it had a length of 100 kilometers and this fault brought a magnitude 7.4 to the media. When Barka measured the beat in Adapazarı, he measured beats with a length of 4.85 cm. Therefore, the magnitude of an earthquake is also related to the pulse. Therefore, in the light of these data, I think the magnitude of the possible Istanbul earthquake will not exceed the range of 7.2 to 7.4. It should not be over 7.4, because at a 5-meter throw, a 100-kilometer benefit does not seem possible to have an earthquake over 7.4.”
40 PERCENT OF THE ANATOLIAN SIDE AND 60 PERCENT OF THE EUROPEAN SIDE SHOULD BE RESTRUCTURED
Selim also included the Asian and European sides of Istanbul in his evaluations, and added: “On the Anatolian side, there are places with very solid grounds and building stock, but there are also places with weak ground and building stock. To put it almost, unfortunately, 40 percent of the Anatolian side should be prepared for an earthquake with an estimate of three or five. Of course, there are different opinions on this subject, but I am talking about Tuzla and Kadıköy. When you look at the European Side, on the contrary, the situation is a little more, due to the density of the population and the differences in the building stock, 60 percent is almost in bad condition and needs to be renewed.
Emphasizing that the ground and solid building factors are very important even if the regions are under risk and that the demolitions will be accordingly, Selim said: “In the earthquake that hit İzmir, the active faults on the land did not have an effect. On the other hand, there are no faults in Istanbul that could produce earthquakes of this magnitude. The northern branch of the North Anatolian Fault will work. Therefore, building-building relationships will arise with this weak ground. Of course, all buildings in the risky area cannot be demolished. The same happened in the earthquakes in Izmir and Adapazarı, perhaps one or two of the buildings in the same site, made of the same material from the same contractor, were demolished. Soils have some behavior against earthquake waves. In all of them, the buildings may not be demolished. However, strengthening the buildings is the most important pre-earthquake precaution, where local governments and our people should be in cooperation. Urban transformation planning should be implemented as soon as possible. As residents, let's get service from local authorities and help them.”
CONTSTRUCTION OF BUILDIND ACCORDING TO THE GROUND IS IMPORTANT
Stating that a quality building can survive even on a weak ground, Selim said: “It is beneficial to construct the building according to the ground here, whether the floors are strong or weak. They also have techniques; If you build bored pile system, raft foundation, tunnel formwork, curtain concrete, that is, a quality building, that building will survive on a weak ground. The main risk is corrosion on reinforcements or buildings that are 35-40 years old, not renovated.”
WE CAN NEVER DETERM THE TIME OF EARTHQUAKE
Adding that time estimates regarding the earthquake are not possible, Selim said, “Science is not in a place where the earthquake time can be given. It is very wrong to give time to scientific studies. Therefore, it is not clear when the fault will operate. However, after 1999 earthquake this 115-kilometer segment carries a risk, its maximum effect will be 7.4 and the minimum will be 7.2. But we can never give time.”
GREAT EARTHQUAKE CAN BE PRECURSED
At the end, Selim stating that as in previous earthquakes, smaller earthquakes can be precursors before major earthquakes and that some earthquakes can prevent large earthquakes, finished his words with the following:
“The occurrence of many earthquakes of 6 magnitude will of course affect 7 and above earthquakes. More precisely, the occurrence of too many earthquakes of 6 magnitude will prevent an earthquake of 7 or more. There are many studies on pre-earthquake reporting, but there are some earthquakes that have also occurred in our country, one of them is the 1971 Burdur Earthquake; There was an earthquake around 7, 1 minute before it has a precursor. Again, in the 1964 Manyas Earthquake, a 5.1 pioneer took place 1 and a half minutes ago. Not every earthquake tells or does not tell this, but if there is an earthquake of 5.9 or 6.0 in the Sea of Marmara, you need to think a little, realize that this is a pioneer, and if an earthquake of this magnitude occurs, it is necessary to be careful considering that it may come. Two months after the 1999 earthquake, a 5.8 earthquake occurred in Sapanca. I was in Izmit at that time and I left Izmit immediately. The next day, 12 November 1999, an earthquake of 7.2 occurred in Düzce. We can say that the 5.8 earthquake was actually the precursor of the great earthquake. But this situation is not always experienced. It is necessary to analyze this well.