When a 7.8 magnitude earthquake struck southeastern Turkey and northwestern Syria early Monday morning local time, its tremor could be felt as far afield as Lebanon, Cyprus, Greece, Israel, and the Palestinian territories. A second quake, which recorded a magnitude of 7.5, struck just 9 hours later.
Both countries at the center are still reeling from the devastating aftermath, rescue workers on the ground tell TIME. So far, 11,200 people have been killed as a result of the quakes, and tens of thousands more have been injured. Thousands of buildings have also been reduced to rubble.
Though earthquakes are not uncommon in this part of the world, this week’s are believed to be the largest and deadliest to hit Turkey in decades. Here’s what we know so far.
When and where did the earthquakes in Turkey occur?
The initial earthquake struck the southern Turkish city of Gaziantep, roughly 150 miles away from the Turkey-Syria border, at 4:17 a.m. local time at a depth of about 11 miles, according to the U.S. Geological Survey. The second earthquake, the epicenter of which was roughly 80 miles north of Gaziantep in Turkey’s Kahramanmaras province, struck at 1:24 p.m. local time and was six miles deep, according to USGS.
More than 300 aftershocks rumbled after the initial quakes, according to Turkey’s Vice President Fuat Oktay.
How big is a 7.8 quake on the local magnitude scale?
While an earthquake magnitude of 2.5 or less can pass by undetected, earthquakes with a magnitude of 7.0 or higher are classified as a “major earthquake,” which can cause serious damage. A magnitude 8.0 or higher, considered “a great earthquake,” is capable of destroying entire communities.
While the magnitude of an earthquake denotes its size and strength, the potential damage caused by a quake is also determined by its depth (the shallower the quake, the more damaging) and its proximity to population centers.
In a tweet, U.S. Geological Survey seismologist Susan Hough likened the size of the initial earthquake in Turkey to San Francisco’s Great Earthquake of 1906, which left more than 3,000 dead and much of the city in ruin.