Earthquake Aftershocks May Rock Turkey and Syria for Months, Even Years

early Monday morning, A 7.8 magnitude earthquake struck Turkey and Syria, followed nine hours later by a 7.5 magnitude aftershock. The death toll is over 3,800 and rescuers have only just begun combing through the collapsed buildings.

Aftershocks will continue to shake the area as local faulting adapts to such a powerful initial tremor, and scientists say this process could take months, if not years, instead of days. There is even a possibility – albeit a small one – of an aftershock greater than the original tremor.

“The risk of aftershocks is essentially greatest right after the main tremor, but there will be noticeable aftershocks after this earthquake for years to come,” said David Oglesby, a geophysicist at the University of California, Riverside. “Right now I can predict for you that there will be many more magnitude 5, probably magnitude 6 or so aftershocks in this area. It’s an easy decision because historically, statistically, it’s almost guaranteed.”

That will make a humanitarian crisis in Turkey and Syria even more horrifying. “We can’t tell people: OK, it’s good, you’re done. That was terrible and now it’s over. Because that’s just not how the earth works,” says earthquake geologist Wendy Bohon. “It really sucks to know that after being so traumatized and going through such a devastating experience, these people have to be shaken by earthquakes for a long time.”

Earthquakes are products of plate tectonics: plates are large masses of rock that move independently in the earth’s crust but touch along faults. “Eventually, the stress and strain will overcome the friction holding the rocks together, and those rocks will fracture in an earthquake,” says Bohon. “When the rocks break, they release energy in the form of waves, and we feel those waves as tremors.”

Monday morning’s main tremor struck about 125 miles along the East Anatolian Fault, a known fault line in southern Turkey. More specifically, it was a “strike-slip” earthquake, meaning that stresses built up between two horizontally moving masses of rock until the fault ruptured. It was also very shallow underground, meaning more intense tremors occurred on the surface. (The San Andreas Fault in California is also a fault—it was the one that virtually destroyed San Francisco in 1906.)

In general, the larger the main tremor, the larger the aftershocks, which tend to decrease in frequency and severity over time. As you can see on this map, aftershocks of varying intensities swarmed along the original tremor’s fault line, as well as another but connected fault line to the north, where the magnitude 7.5 aftershock appears to have struck. “It’s a really complicated fault system because the crust is really fractured there,” says Alice Gabriel, a seismologist at the Scripps Institution of Oceanography.

This complexity means that what happens in a bug doesn’t stay there. It may be that the stress that led to the magnitude 7.5 quake had been building for some time and the jolt from the main tremor unleashed it. “It kind of put its clock back a little bit so that it had the big earthquake, which it probably would have had a little earlier anyway,” says Austin Elliott, an earthquake geologist with the United States Geological Survey. Such aftershocks are “just different earthquakes – there is nothing that makes them different. It’s just that an earthquake that big changes the stress in the earth’s crust so much that it increases the rate of all other earthquakes locally.”