Earthquakes are a natural phenomenon that takes place in the lithosphere layer of the earth. Ones have occurred in many parts of the planet so far, and thousands of people have lost their lives due to negligence. One of the major earthquakes that happened closest to today is the Kahramanmaras earthquakes, with 7.9 and 7.8 magnitudes that occurred on February 6, 2023, in Türkiye, affecting 11 cities. In these earthquakes, nearly 50,000 deaths have been officially recorded so far.

Due to its earthquake history, Japan is known as the most earthquake-prepared country in the world compared to other countries. Tokyo Metropolitan Municipality announced that it would take measures against a very severe earthquake, with a magnitude of 9.0, which may occur in Tokyo until 2030. This plan aims to reduce life and property damage by 30% by reinforcing buildings.

Skopje too is in the earthquake zone. It has been severely damaged by earthquakes many times throughout history. The last devastating earthquake was on July 26, 1963, with a magnitude of 6.1, but it was 6.9 on the Richter scale that we use today. It was 6 meters deep and killed 1070 people by demolishing around 80% of the city.

Despite being in the Cold War years, more than 80 countries mobilized with the call of the Socialist Republic of Macedonia, and Skopje was rebuilt again. As an appreciation, Skopje named its streets and buildings after the states that built them. The urban plan for a modern Skopje was designed in 1965 by Japanese architect Kenzo Tange, who won the international competition to rebuild the city center. In 1969, the world’s first rubber seismic isolation structure was implemented by Swiss engineers in the Elementary School “Johan Heinrich Pestalozzi” building in Skopje, Macedonia.

On the 60th anniversary of the earthquake, a question remains in mind: How ready is Skopje, where the majority of the city is dominated by old buildings built years ago according to the technology of that time, against possible new earthquakes? And which type of prevention can we take to reduce the risk to a minimum level?

First of all, experts say that the lifespan of a building can vary between 30-50 years up to 100 years, depending on the material quality. A 30-year-old building can be even more potent than newer buildings if it’s built with quality. The lack of necessary precautions as insulation shortens this life. For example, the average age of facilities that need to be demolished in Istanbul is 26.3 years.

The factors affecting the earthquake risk factor of buildings are as follows:

Soil survey: Instead of doing a soil survey according to the building, the building should be done according to the soil survey. It is also essential that there is no groundwater on the floor of the building. Due to the risk of liquefaction, soft soil such as stream beds and fill areas is risky to build on. Because such floors increase the intensity of the earthquake wave much more than rocky floors, creating a security weakness for the building. Therefore, the new settlements to be reconstructed should be decided by carrying out the necessary soil survey studies. If possible, rocky ground areas should be preferred.

Quality of building materials and inspection: Inspection should be done thoroughly and correctly, and the company that made the construction should not be able to choose the company that will carry out the inspection. The structure should be in accordance with the project, and arrangements such as column cutting, wall removal, and illegal story adding should be avoided. Concrete and steel must be produced under the required quality standards. In past examples, it has been observed that the sea gravel and sea sand in the concrete content used in some earthquake zones reduce the concrete quality.

Column and beam condition: Cracks on columns and beams can give information about the durability of the building. But even if there are no cracks in these areas, this does not mean that the durability of the building is high. An earthquake resistance test can only obtain the most accurate result.

Experts recommend that an earthquake resistance test be carried out in the event of dampness in the basement as this may damage the structural systems, cracks in columns or beams, or if buildings have shops on the ground floor. Facilities that do not have sufficient durability are reinforced by different techniques or rebuilt with urban transformation and made more suitable and robust for today’s conditions.

In the tests, first, the plan of the building is drawn, and its static conformity is examined. While testing the durability, experts first look at the building’s floor and carrier systems. The ground condition of the building, its distance from the fault line, and the earthquakes it has experienced are examined. With the X-ray technique, it is learned how often iron and beam columns are used. When necessary, a core sample is taken from the concrete, and various pressure tests measure the durability of the concrete.

Reinforcement is the first option as it costs less than rebuilding. Different reinforcement techniques are used, such as steel and column sheathing, adding wings, epoxy injection, and cladding with carbon fiber material. As a result of the tests, if it is understood that the reinforcing will not be enough, however costly, the buildings should be demolished and rebuilt under the scientific light of today’s engineering, such as inspection, ground survey, and material quality. Because life is more valuable than the cost of any building, and an earthquake is always with us like a bomb that may explode at any time. Let’s hope to reach the day when earthquakes are no longer considered natural disasters that take lives.

Hakan Yağcı
Reşit Efe Bayram

Sources:
Bbc: “Japonya’da Büyük Depremler Nasıl Az Hasarla Atlatılıyor? (How Major Earthquakes Survive with Little Damage in Japan)”
ResearchGate: “Damaging Effects of July 26, 1963, Skopje Earthquake”
Discovering Macedonia: “The Skopje Earthquake – a devastating catastrophe.”
Indigo Dergisi: “Deprem dayanıklılık testi nedir? Nasıl yapılır? (What is an earthquake endurance test? How to do it?)”
BCI Construction: “Which Factors Determine the Lifespan of a Building?”
Dergipark: “Türkiye’deki Depremlerde Alınan ve Alınabilecek Önlemler (Taken and Need to Take Precautions in Turkey’s Earthquakes)”
Mapfre: “Binanın Depreme Dayanıklı Olduğu Nasıl Anlaşılır? (How to Tell if the Building is Earthquake Resistant)”
Intac Insaat: “Reinforcement of Buildings”