Those traveling to earthquake-hit Turkey and Syria to help are finding a region that has gone haywire. Everything possible is broken, crushed or grotesquely shifted. The injuries are everywhere: in the landscape, on the buildings and of course on the people. It’s a nightmare.
Doctors try thousands Broken arms and legs, contusions, organ failure and bleeding to treat. Engineers go house to house to inspect buildings that have not toppled or collapsed, just cracked or warped. Often with just hammers and their naked eyes, they decide if they are safe enough for their residents to return. And then there are the geoscientists. You will find a changed landscape: Within seconds, ditches are torn open, today in some places they are several hundred meters wide and deep. Olive groves were divided as if by a mighty hand, roads were shifted by several meters, which is why one end no longer wants to fit the other.
Seismologists, geomorphologists and tectonists from all over the world are studying the February 6 earthquake and its thousands of aftershocks. They collect data using seismometers and satellite measurementsto learn from the tragedy – more than 50,000 dead, five million people had to leave their homes – and to be better prepared for future earthquakes, such as those expected in front of Istanbul or Los Angeles. “The dramatic effects are a clear warning for other high-risk seismic areas in Turkey and beyond,” says Marco Bohnhoff from the Geoforschungszentrum (GFZ) in Potsdam.
How could there be two earthquakes of almost equal magnitude in quick succession?
Less than two weeks after the quake, a research team from Turkey, Greece and the USA already has a first study on the preprint server EarthArXiv published, awaiting peer review. In it, the scientists have reconstructed the course of the earthquake. The first major 7.8-magnitude tremor originated in a fault that had not yet been mapped. Only then did it jump over to the East Anatolian Fault, which ruptured 350 kilometers in length.
The riddle also seems to have been solved, as not even one day after the main tremor with a magnitude of 7.8, an earthquake with a magnitude of 7.6, which was almost as strong, could occur further north. It is actually to be expected that aftershocks will decrease in magnitude by about one magnitude. Accordingly, a 7.8 main tremor should be followed by a 6.8 aftershock. But the second big quake could a separate tremor on a separate fault have been – the so-called Sürgü Fault. The tectonic energy had already accumulated there beforehand, explains Bohnhoff. Calculations would show, however, that the first major tremor had redistributed stresses and thus accelerated the “seismic cycle” of the Sürgü fault. “The second earthquake would have occurred anyway,” says the geophysicist. “Only later.”
Could such stress shifts also trigger a severe earthquake near Istanbul, which geoscientists expect there in the near future? Finally, the North Anatolian Fault there borders at its eastern end almost on the northern end of the East Anatolian Fault. “Initial results show that the recent earthquakes are not close enough to the North Anatolian Fault to significantly change the stress field there,” says geologist Derya Guerer from the University of Queensland in Brisbane.
Nevertheless, the winding paths of the earthquakes could provide lessons for other danger zones. It doesn’t matter whether it’s Kahramanmaraş, Istanbul or San Francisco – they are all due to comparable faults on which two tectonic plates slide sideways on each other, locking and deforming until the stress is so great that it exceeds the strength of the rock. Then the pent-up energy is released in one go. The earthquakes in Turkey and Syria are now prompting US geologists to investigate whether a similarly powerful earthquake could also occur in one of the branches of the San Andreas fault. as the New York Times reported. No major earthquake has occurred in its southern section since 1857. And there are also numerous side faults.
But just knowing where a major earthquake is lurking in the near future is useless if city planners and residents don’t take it to heart. Bohnhoff therefore sees the key lesson for Istanbul and other megacities in seismic high-risk areas as being to convert houses and infrastructure as quickly as possible and to comply with the building regulations for new buildings. This is a financially and logistically extremely demanding, but unavoidable task. After all, it is not earthquakes that kill people, but buildings that cannot withstand the tremors.