A magnitude 7.8 earthquake that struck Turkey and Syria early Monday morning has unleashed a cascade of destruction, as powerful aftershocks rocked the region and killed thousands.
After a magnitude 6.7 aftershock of the first quake at around 4 local time; then, nine hours later, another huge shock hit, magnitude 7.5, magnitude 7.5 to the north, followed by smaller aftershocks. These former mobs are destructive in their own right, causing buildings to collapse and destroying an ancient Roman castle, putting people in constant danger. And unfortunately, this may just be a taste of what the region will be dealing with for many months to come.
“The number of aftershocks will decrease over time, but large events can continue, for months or longer,” Jacha Polet, a geophysics researcher at Cal Poly Pomona, tweeted Monday morning. And experts on social media and in the press he expressed similar views.
According to the US Geological Survey, the region where the quake occurred is seismically active, but the area has only experienced three other earthquakes of magnitude 6 or higher since 1970 – most recently, a magnitude 6.7 earthquake that killed thousands and thousands injured in 2020. A magnitude 7.0 earthquake struck Aleppo, Syria in 1822 and killed thousands. Aftershocks were felt up to a year later.
To understand why the region may be at risk for a long time after the initial event, we need to unpack how the earthquake happened in the first place. The region sits atop what is known as the East Anatolian Fault, a strike-slip fault defined as two blocks of rock sliding past each other. People who live across the Pacific Ocean should already be familiar—the San Andreas Fault is another example of this type of fault.
Judith Hubbard, a structural geologist at Nanyang Technological University in Singapore, explained on Twitter as the Arabian Plate collides with the Eurasian Plate to the north, the Anatolian Block leaves out west, “like a watermelon seed out of your fingers.” The East Anatolian Fault is located at the intersection of the Anatolian Block and the Arabian Plate, which is moving about 15 millimeters relative to each other per year, stretching the Earth’s crust across the fault.
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“The tectonic movement between earthquakes is slow but not the ‘catch up’ – it’s that quick movement that causes the seismic energy to come off the fault, causing the Earth to shake,” Hubbard wrote.
Major earthquakes are usually followed by hundreds or thousands of aftershocks that occur along and near the fault that was displaced during the mainshock, according to the Consortium of Incorporated Research Institutes for Seismology.
“With rare exceptions, every magnitude 7 to magnitude 9 earthquake has a collection of smaller aftershocks that can occur for weeks, years, or even centuries after the aftershock,” the consortium said in a video in 2019.
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The ‘mainshock’ of an earthquake refers to two tectonic plates overcoming friction to slide over each other. Aftershocks, by contrast, are typically “fine adjustments of the portion of the fault that collapsed during the main event,” according to the USGS, which is listing nearly 60 aftershocks in the region as of Monday morning. In Turkey, it appears that some of these aftershocks are not occurring along the same fault line as the mainshock, but one sparking off.
Another important factor is depth: Shallow earthquakes are more likely to actually cause earthquakes than those that occur more than 18 miles underground. The epicenter of this earthquake occurred about 10.5 miles underground, Curtin University earth and planetary sciences researcher Chris Elders said Al Jazeera English.
The full scope of the disaster is yet to be realized. Many people still need to be rescued, and many more will be at risk as more missiles hit the region in the coming weeks and months.
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