Turkey earthquake: The science behind the disaster
A seismologist explains
Turkey’s massive 7.8-magnitude earthquake left hundreds dead and thousands injured, followed by an equally powerful 7.5-magnitude aftershock about 12 hours later to wipe out what was left standing and endanger the lives of rescue workers, while the list of the dead so far has reached 2,000 people.
Seismic waves were detected around the world, even by seismographs in the US. The reason there was such a strong earthquake in this part of south-eastern Turkey near the border with Syria has a scientific explanation, offered by professor of geological sciences Jenny Jenkins, of Durham University.
This particular area is located where not two but three tectonic plates intersect. Anatolia, Arabia and Africa. The Arabian plate is moving north towards Europe, “pushing” the Anatolian plate to the west. The movement of the plates creates pressure in fault zones, and the sudden decompression of this pressure causes earthquakes. This particular earthquake probably took place on one of the large faults between the two plates.
Although the region is often plagued by earthquakes, this one surpassed all previous ones. The US Geological Survey pointed out that only three earthquakes larger than 6 on the Richter scale have occurred within 250 kilometers of the site in the last 50 years. And because the Richter scale is exponential, the current magnitude 7.8 earthquake released twice as much energy as the previous recorded magnitude 7.4 earthquake. In fact, in relation to the typical earthquakes that take place in the region and are at 5 Richter, the 7.8 Richter earthquake released 6,000 times more energy .
We usually tend to think of earthquakes as coming from a specific point, the epicenter. They are actually caused by movement across the fault area. The bigger the earthquake, the bigger the area of the fault that moved. For a magnitude 7.8 earthquake, there may have been movement 190 kilometers long and 25 kilometers wide. The earthquake caused material damage at a distance of 80 kilometers northeast of the boundaries of the tectonic plates, while it was also felt in Ankara (815 kilometers), Baghdad (800 kilometers) and Cairo (950 kilometers).
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Aftershocks come to correct changes in the pressure of the tectonic plates and can continue months or even years after the earthquake. Within 11 minutes of the big earthquake, southeast Turkey was hit by two aftershocks of magnitude 6 and 6.7, while 12 hours later came a magnitude 7.5, further north but close to the Surgu fault. Technically it is strong enough to be considered a separate earthquake, however it is believed to have been caused by the first earthquake. But it will also produce its own series of aftershocks.
