Turkey hit by series of powerful earthquakes

Subject: Geography

Section : Physical Geography (Geomorphology )

Concept:

More than 2,000 people have been killed and thousands injured by a huge earthquake which struck south-eastern Turkey, near the Syrian border.
The earthquake, which hit near the town of Gaziantep, was closely followed by numerous aftershocks – including one quake which was almost as large as the first.
Turkey’s President Recep Tayyip Erdogan said the earthquake that hit the area around Gaziantep, was the country’s worst disaster since Erzincan earthquake, 1939.

Erzincan earthquake

The Erzincan earthquake measured 7.8 on the Richter scale, occurred on the North Anatolian Fault Zone (NAFZ), and created a 360-km-long surface rupture.
It killed about 33,000 people and caused extreme damage in the Erzincan Plain and the Kelkit River Valley.

Earthquake

An earthquake is an intense shaking of the ground caused by movement under the earth’s surface.
It happens when two blocks of the earth suddenly slip past one another.
This releases stored-up ‘elastic strain’ energy in the form of seismic waves, which spreads through the earth and cause the shaking of the ground.
The location below the earth’s surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the

Causes of earthquake

The earth’s outermost surface, crust, is fragmented into tectonic plates. The edges of the plates are called plate boundaries, which are made up of faults.
The tectonic plates constantly move at a slow pace, sliding past one another and bumping into each other.
As the edges of the plates are quite rough, they get stuck with one another while the rest of the plate keeps moving.
Earthquake occurs when the plate has moved far enough and the edges unstick on one of the faults.

How are earthquakes measured?

They are measured on a scale called the Moment Magnitude Scale (Mw).
This has replaced the Richter scale (magnitude scale), now considered outdated and less accurate. Richter scale relates to the energy released during the earthquake which is expressed in absolute numbers, 0-10.
The intensity scale/ Mercalli scale takes into account the visible damage caused by the event. The range of intensity scale is from 1-12
The number attributed to an earthquake represents a combination of the distance the fault line has moved and the force that moved it.
A tremor of 2.5 or less usually cannot be felt, but can be detected by instruments.
Quakes of up to five are felt and cause minor damage.
The Turkish earthquake at 7.8 is classified as major and usually causes serious damage
Anything above 8 causes catastrophic damage and can totally destroy communities at its centre.

Can earthquakes be predicted?

An accurate prediction of an earthquake requires some sort of a precursory signal from within the earth that indicates a big quake is on the way.
Moreover, the signal must occur only before large earthquakes so that it doesn’t indicate every small movement within the earth’s surface.
Currently, there is no equipment to find such precursors, even if they exist.

Reasons for earthquakes in Turkey

The region where the earthquake has struck lies along a well-known seismic fault line called the Anatolia tectonic block.
It is a seismically active zone — though not as active as, say, the Himalayan region.
The seismicity in this region is a result of interactions between the African, Eurasian, and Arabian plates.
In the present case, it was the Arabian plate moving northwards and grinding against the Anatolian plate.
Also, the present earthquakes emerged from relatively shallow depths which made them devastating.
Shallow earthquakes are generally more devastating because they carry greater energy when they emerge on the surface.

Due to faultlines running across Turkey’s southeast and north, the country has always been a hotbed of seismic activity

Turkey is a hotbed of Seismic activity

In the eastern Mediterranean region comprising Turkey, Syria and Jordan, tectonics are dominated by complex interactions between the African, Arabian, and Eurasian tectonic plates, and the Anatolian tectonic block.
Dominant structures here are:
Red Sea Rift, the spreading centre between the African and Arabian plates;
Dead Sea Transform, a major strike-slip fault (explained in the diagram below) that also accommodates Africa-Arabia relative motions;
North Anatolia Fault, a right-lateral strike-slip structure in northern Turkey accommodating much of the translational motion of the Anatolia block westwards with respect to Eurasia and Africa;

Cyprian Arc, a convergent boundary between the Africa plate and the Anatolia block.
A convergent plate boundary is formed when tectonic plates crash into each other. They are also known as destructive boundaries.