A devastating earthquake, with its magnitude measuring 7.8 in the Richter Scale, followed by three strong tremors, rocked wide swaths of Turkey and Syria at 4:17am (local time) on February 6, 2023, killing more than 37,000 people (as on February 14). According to the US Geological Survey (USGS), the epicentre of the 7.8-magnitude quake was 23km east of Nurdagi in Gaziantep, at a depth of 24.1km. The earthquake devastated neighbouring Syria, as well. Between 11 and 15 minutes after the first tremor, another earthquake took place near the Turkey-Syria border, and it was followed by the third and fourth quakes. As the earthquake triggered the collapse of several multi-storeyed buildings, thousands of people were trapped under the rubble. It may be noted that Turkey experienced strong earthquakes quite a number of times, in the past. Geologists are of the opinion that the geographical location of the country is one of the reasons.
Usually, Tectonic plates, while shifting their positions, cause earthquakes. As Turkey is located at the intersection of four tectonic plates, it is in the list of most earthquake-prone countries. Most of this country lies on the Anatolian Tectonic plate, which is again located between the Eurasian, African and Arabian Tectonic plates. The Arabian plate continuously collides with the Anatolian plate that rotates anti-clockwise. According to geologists, repeated collisions between the Arabian plate and the Anatolian plate prompt the latter to collide with the Eurasian plate. Continuous collisions between these plates often trigger earthquakes in Turkey. Interestingly, a fault line, called North Anatolian Fault Line (NAF), has been formed where the Anatolian plate meets the Eurasian plate, in particular. The NAF is an active right-lateral strike-slip fault in northern Anatolia, and a transform boundary between the Eurasian plate and the Anatolian plate. The fault extends westward from a junction with the East Anatolian Fault at the Karliova Triple Junction in eastern Turkey, across northern Turkey and into the Aegean Sea for a length of 1,500km.
Geologists have said that large earthquakes are caused by huge collisions along a fault line, which is the meeting point of two or more Tectonic plates. However, moderate and mild earthquakes are caused by any movement along the centre of Tectonic plates. As far as Turkey’s geographical position is concerned, it is situated in the middle of three Tectonic plates. Although most of Turkey lies on the Anatolian plate, the northern part of the country sits on the Eurasian Tectonic plate, the southern part on the African Tectonic plate and the eastern part lies on the Arabian Tectonic plate. Hence, two major fault lines – East Anatolian and North Anatolian – have been created in that region. These two fault lines are highly prone to vibration. When the Arabian plate moves northward to the Eurasian plate, pressure increases on the Anatolian plate, and pushes it westward to the Aegean Sea. The February 6 earthquake in Turkey took place on the south-western edge of the East Anatolian fault line. While the epicentre of the first quake was 18km below the surface, the second was at a depth of 10km.
According to geologists, NAF is the source of most earthquakes in the world. The worst earthquake of history occurred in 1960. It hit at 3:11pm (local time) approximately 160km off the coast of Chile, parallel to the city of Valdivia. The shock is generally agreed to have had a magnitude of 9.5, although some studies alternately proposed that it might have been 9.4 or 9.6. The temblor had lasted for 10 minutes, causing substantial damage and loss of life both in the Latin American country. It had also generated tsunamis in distant Pacific coastal areas.
While 95% of Turkish territory is earthquake-prone, one-third of the country is at the highest risk. The high risk zones include most of Istanbul and İzmir, and the eastern part of Anatolia (historically known as Asia Minor). The Disaster and Emergency Response Force of Turkey has claimed that the country has experienced more than 33,000 quakes since 2020, and 332 of them, measuring 4 or more on the Richter Scale, had a great impact. The devastating February 6 (2023) earthquakes have brought back the old memories.
Meanwhile, seismologists have claimed that Turkey may have moved 20ft west because of these quakes, which badly damaged the 225km-long fault line between the Anatolian and Arabian Tectonic plates. According to Italian Seismologist Professor Carlo Doglioni, initial estimates suggest the quakes may have led to Turkey having “slipped by five to six metres (or 20ft) compared to Syria“. He said: “A more accurate analysis is pending information from satellites.” The Professor explained: “The massive laceration involved an area 190km long and 25km wide… violently shaking the ground and causing a sequence that reached the two most intense peaks (that were) nine hours apart.“
For his part, Dr Bob Holdsworth, a Professor of Structural Geology at Durham University, stressed that the plate shift was “perfectly reasonable“, considering the magnitude of the earthquake. He told the Daily Mail: “There is a fairly predictable, widely documented relationship between the magnitude of an earthquake and the typical offset that occurs. As a rule of thumb, a magnitude 6.5 to 6.9 event is associated with an offset of around one metre – whilst the largest known earthquakes can involve offsets of 10 to 15mt.” Dr Holdsworth added: “The faults that slipped (on February 6) in Turkey are strike-slip faults that involve mainly horizontal displacements, and so the overall offsets in the region of 3-6mt proposed here are perfectly reasonable.“
As far as the intensity of the earthquakes is concerned, the geologists are of the opinion that it could trigger a prolonged seismic epidemic and continue for days or months, if not years, as has happened in some cases in the past.
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