Earthquake in Turkey, Syria: Why earthquakes happen, how are they measured, what makes Turkey earthquake-prone

Turkey-Syria earthquake: Turkey was hit by a series of devastating earthquakes on Monday, 6 February. The death toll reached more than 5000 on Tuesday, with many more being injured and displaced. The number of victims of these earthquakes is expected to rise. Pictures coming out of Turkey and Syria as emergency workers rescue people from the rubble are heart-wrenching and horrifying. Temperatures in the affected areas are also playing on the enemy side and are frequently dropping below freezing.

The epicentre of the 7.4 magnitude earthquake was located in the Turkish province of Kahramanmaras near the Syrian border. Another 6.6 magnitude earthquake was measured shortly after in Gaziantep province of Turkey.

Turkey is known to be prone to earthquakes, lying as it does at the junction of three tectonic plates, Eurasian, Arabian and African. These plates move a couple of centimetres (approx. 1 inch) every year. Two tectonic plates can move away from each other, toward each other or sometimes up against each other, causing the continent above them to move. These movements are called plate tectonics which is the cause of an earthquake.

Why do earthquakes happen?

One of the major causes of an earthquake is a slip along a fault, which is a junction between two tectonic plates. Such earthquakes are called inter-plate earthquakes. Another cause is the movement of tectonic plates; such earthquakes are called an intra-plate earthquakes.
When two plates grind against each other, a large amount of pressure builds up. When this pressure becomes too great, it is released in the form of an earthquake. The shaking caused by the release of energy travels through the Earth's surface, causing the ground to shake. This movement of the Earth's surface can cause damage to buildings, roads, and other structures.

How earthquakes are recorded?

Earthquakes are recorded using an instrument called a seismograph and the recording that they make is called a seismogram. The seismograph has a base that sets firmly on the ground and a heavy weight that hangs free. When an earthquake causes the ground to shake, the base of the seismograph shakes too, but the hanging weight does not. Instead, the spring or strings that are hanging from above absorbs all the movement. This difference in position between the shaking part of the seismograph and the motionless part is what is recorded.

How earthquakes are measured?

It is common to associate the severity of an earthquake with its size, or magnitude. A more accurate indicator of damage, however, is the earthquake’s intensity at each location rather than its magnitude, which is measured at the source.

The seismograph recordings made on the seismograph at the surface of the earth determine how large the earthquake was. A short wiggly line that doesn’t wiggle very much means a small earthquake, and a long wiggly line that wiggles a lot means a large earthquake. The length of the wiggle depends on the size of the fault, and the size of the wiggle depends on the amount of slip.

Why is Turkey prone to earthquakes?

This is not the first time that Turkey has experienced seismic activity, in 2020 itself, it recorded almost 33,000 small earthquakes in the region. According to Disaster and Management Authority (AFAD), out of these 33,000 earthquakes, 332 were of magnitudes more than 4.0.

Turkey is located on the Anatolian tectonic plate, which is wedged between the Eurasian and African plates. On the north side, the minor Arabian plate further restricts movement. One fault line, the North Anatolian fault (NAF) line, the meeting point of the Eurasian and Anatolian tectonic plates, is known to be “particularly devastating”. The NAF, one of the best-understood fault systems in the world, stretches from the south of Istanbul to northeastern Turkey and has caused catastrophic earthquakes in the past.

In 1999 it caused two earthquakes, of 7.4 and 7.0 magnitude each, in Gölcük and Düzce provinces. Almost 18,000 people died and more than 45,000 were injured. In 2011 again, more than 500 people died when a 7.1 magnitude earthquake shook the eastern city of Van.