How did this catastrophic scale come about?
It is a catastrophe of historic proportions: the earthquake in the Turkish-Syrian border area. The region is considered one of the most active earthquake zones in the world. But the earth hasn’t trembled so violently there for a long time. 1144, almost 1000 years ago, is said to have been the last earthquake of a comparable magnitude of 7.7.
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Now, early Monday, February 6, a 7.8 magnitude earthquake struck this region at 1:24 p.m a second severe earthquake of magnitude 7.5 followed: Thousands of houses collapsed, more than 5000 people lost their lives, 13.5 million people are at least indirectly affected, so far there have been over 200 aftershocks. How did it come to such devastating proportions?
Crumple zone of several continental plates
Earthquakes are caused by plate tectonic movements. The earth consists of seven large and several small moving plates. One of the largest is the Eurasian Plate, on which Germany also lies. Several plates meet in the affected Turkish-Syrian border area: the Eurasian, the Anatolian and the Arabian.
“The northward collision of the Arabian Plate in Eurasia is pushing the intervening Anatolian Plate westward at a rate of about two centimeters per year,” explains British geoscientist David Rothery.
The friction along the fault lines (also called faults) builds up local stresses over the years – until the accumulated stress is great enough to overcome the resistance and the rock masses collide with a sudden jolt. This is the moment when an earthquake occurs. One reason for the severity of the quake is that the last one was so long ago. So much tension could build up.
Shallow depth and great energy
In addition, the earthquake occurred at a depth of only 17.9 kilometers – the distance to the earth’s surface was therefore comparatively small. “The combination of high magnitude and shallow depth made the quake extremely destructive,” says British Professor of Civil Engineering and Seismology Mohammad Kashani.
Also, much more energy has been released, compounding the magnitude. “The 7.8 magnitude earthquake in Turkey released about 250 times more energy than the 6.2 magnitude earthquake that struck Amatrice in central Italy on August 24, 2016 and claimed 300 lives,” says Joanna Faure Walker, Director of the UK UCL Institute for Risk and Disaster Management. “The increased strength and energy released means a much larger area is affected.”
Thousands dead after earthquake disaster in Turkey and Syria
Numerous countries have pledged support, and aid teams from Germany have also set off.
© Source: dpa
The magnitude scale, which measures the strength of earthquakes, is not linear. “Each step up corresponds to 32 times the energy released. This means that a magnitude 7.8 tremor releases about 6,000 times more energy than the more moderate magnitude 5 tremors that typically occur in the region,” writes geoscientist Jenny Jenkins (Durham University) in one Guest Contribution for “The Conversation”. The earthquake was 190 kilometers long and 25 kilometers wide, and the tremors could be felt as far as Cairo, Egypt, 950 kilometers away.
Another factor is the local infrastructure. In the past 50 years, the world’s deadliest earthquakes have occurred in Turkey. But that wasn’t because the tremors were the strongest. “The death toll depends not only on the extent of the disaster, but above all on the number of people in the affected area and on the quality and construction of the buildings,” says Walker.
Unstable infrastructure in Turkey
There are several metropolises in the Turkish-Syrian earthquake region: the Syrian city of Aleppo and the Turkish cities of Adana and Gaziantep near the epicenter of the quake. Several thousand buildings have already collapsed, and aftershocks could cause more to collapse.
Buildings in Turkey have actually had to meet modern, earthquake-proof standards since 2004. But there are also many older buildings. “The photos show that some of the collapsed buildings may have been built before modern seismic codes and were therefore not adequately designed and engineered to withstand an earthquake of this magnitude,” says Kashani.
And even newer buildings are not earthquake-proof. “Even modern buildings, which should actually be able to withstand an earthquake of this magnitude if the building regulations were complied with, collapsed like a house of cards and buried their occupants under them,” reports RND correspondent Gerd Höhler. Reasons for this are, for example, incorrect static calculations or botched construction. In Syria, the infrastructure was in an extremely bad condition anyway due to the years of civil war.
Could early warning systems have helped?
Turkey is notorious for earthquakes. Tremors occur again and again, especially along the North Anatolian Fault and the East Anatolian Fault (where the earthquake now occurred). The metropolis of Istanbul, for example, is very close to the North Anatolian Fault. The seismologists therefore expect a larger earthquake in the future – they just don’t know when exactly.
Because earthquakes cannot yet be predicted. However, there are early warning systems that measure the so-called primary wave. But it often only takes a few seconds for the destructive secondary wave to appear. That’s not enough to leave the place, but, for example, to switch off electricity and gas lines and thus minimize consequential damage. He reports that Research area Earth and Environment of the Helmholtz Association.
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The earthquake in Turkey and Syria caught people unprepared. “The only warning people had was the long absence of a really big earthquake,” says scientist Martinez Garzon from GZF Potsdam in an interview with the “Märkische Allgemeine Zeitung” (MAZ). In their opinion, an early warning system would hardly have changed anything. Because nothing is known of foreshocks above magnitude 3 and the warning time was too short because Gaziantep was too close to the epicenter of the current quake.
Earthquake prevention: preparation and response
Others, like Turkey’s leading engineer Huseyin Alan, criticize, however, that the government has not taken the warnings seriously enough. For example, an airport lies on a demarcation line. That is completely unacceptable.
Earthquakes cannot yet be predicted with certainty and with sufficient advance notice. According to the British volcanologist Carmen Solana, the severity of an earthquake depends primarily on two factors: preparation (such as earthquake-proof infrastructure) and an effective response.
“Unfortunately, resilient infrastructure is patchy in southern Turkey, and particularly in Syria, so saving lives now largely depends on response,” Solana said.
It is also a warning for western Turkey. Should the forecast earthquake occur, up to 100,000 people could die.