The February 2023 earthquakes in Turkey were caused by a sudden rupture along the East Anatolian Fault Zone, where the Anatolian plate and the Arabian plate grind past each other. Two massive quakes struck just nine hours apart: a magnitude 7.8 at 4:17 a.m. local time, followed by a magnitude 7.7 near Elbistan. The fault had been locked and building pressure for over a century, and when it finally broke, the release of stored energy was catastrophic.
Three Plates Colliding in Southern Turkey
Turkey sits on one of the most tectonically complicated pieces of ground on Earth. The Arabian plate to the southeast and the African plate to the south are both pushing northward into the Eurasian plate. Caught in between is a smaller piece of crust called the Anatolian microplate, which is being squeezed westward like a watermelon seed pinched between two fingers. Geologists call this “escape tectonics,” and it’s been going on for millions of years.
These three plates meet near the Gulf of İskenderun in southeastern Turkey, forming what’s known as the Anatolia-Arabia-Africa triple junction. This junction is geologically unstable and has been migrating to the southwest over the past five million years. Two major fault systems radiate from this collision zone: the North Anatolian Fault (which produced the devastating 1999 İzmit earthquake) and the East Anatolian Fault Zone, which ruptured in 2023.
How the East Anatolian Fault Works
The East Anatolian Fault Zone runs roughly 700 kilometers from northeastern Turkey down to the Mediterranean coast. It’s a left-lateral strike-slip fault, meaning if you stood on one side and looked across, the opposite side would be moving to your left. The Anatolian plate slides southwest relative to the Arabian plate along this boundary at rates that vary from about 10 millimeters per year in the northeast to around 4 millimeters per year near where the 2023 earthquakes struck.
Four millimeters a year sounds trivial, but that motion adds up. When a fault is locked by friction, those millimeters become stored elastic energy in the surrounding rock. The segment that ruptured in 2023 hadn’t produced a major earthquake since an estimated magnitude 7.1 event in 1893. That’s 130 years of accumulated strain. Before that, the largest known earthquakes on the fault occurred in 1114 (estimated magnitude greater than 7.8) and 1513 (greater than 7.4). These long gaps between major quakes are a hallmark of faults that store enormous energy before releasing it all at once.
Why Two Major Quakes Hit the Same Day
The first earthquake, magnitude 7.8, struck at a depth of about 10 kilometers near Pazarcık in Kahramanmaraş province. The rupture tore along the fault with predominantly horizontal, side-to-side motion. Within 11 minutes, a magnitude 6.7 aftershock followed.
Then, about nine hours later, a second major earthquake of magnitude 7.7 struck near Elbistan, roughly 95 kilometers to the north, on a connected but separate fault segment called the Sürgü fault. This wasn’t a typical aftershock. It was a triggered earthquake: the massive stress redistribution caused by the first rupture pushed the already-strained Sürgü fault past its breaking point. The second quake ruptured over 100 kilometers of fault in a primarily east-west direction, with significant shallow motion that made the shaking at the surface especially destructive.
This type of event, two major earthquakes occurring in rapid succession on related faults, is sometimes called an earthquake doublet. It’s relatively rare at this scale and made the disaster far worse than a single event would have been, because buildings weakened by the first quake were hit again before anyone could assess the damage.
What Happened at the Surface
The energy released by these earthquakes physically displaced the ground by extraordinary amounts. GPS stations recorded surface movements of up to 0.3 meters (about one foot) in the southwest direction from the first event alone. But along the fault trace itself, the offsets were far more dramatic.
Detailed drone surveys of the second earthquake’s surface rupture revealed a crack stretching approximately 143 kilometers across the landscape. Researchers measured 538 individual displacement points along this rupture and found an average horizontal offset of 4.1 meters, with a maximum of 10.6 meters near the Ekinözü section. That’s nearly 35 feet of sideways ground movement in a single event. Roads, fields, and walls that once lined up were shifted by the width of a room.
Turkey’s Disaster and Emergency Management Authority (AFAD) recorded over 11,000 aftershocks following the two mainshocks. Many of these were strong enough to cause additional damage and made rescue operations more dangerous.
Why This Fault Was Primed to Break
Seismologists had long recognized the East Anatolian Fault Zone as a major seismic hazard, but the specific segments that ruptured in 2023 had been unusually quiet in the modern instrumental record. Geodetic studies using GPS and satellite radar showed that the fault was locked along much of its length, meaning the plates were moving but the fault itself wasn’t creeping to relieve stress gradually. Instead, strain was accumulating in the rocks on either side.
The slip rate along the fault isn’t uniform. Near the Palu and Pütürge segments in the northeast, rates reach 10 to 15 millimeters per year. Farther southwest, where the 2023 rupture occurred, rates drop below 5 millimeters per year. But even at these lower rates, 130 years of accumulation translates to roughly half a meter of unrelieved slip deficit. When the fault finally broke, it released that deficit all at once, plus additional slip driven by the dynamic energy of the propagating rupture itself.
The rupture also revealed faults that hadn’t been previously mapped. At both ends of the second earthquake’s surface break, researchers identified previously unrecognized fault segments spanning about 25 kilometers combined. This is a reminder that even well-studied fault zones can hold surprises underground.
The Broader Tectonic Picture
The 2023 earthquakes fit into a pattern of seismic activity driven by the ongoing collision of the Arabian and African plates with Eurasia. As the Arabian plate pushes north at roughly 20 millimeters per year, the Anatolian plate has no choice but to move west. This westward escape loads both the East Anatolian and North Anatolian fault systems. The North Anatolian Fault has produced a well-documented sequence of major earthquakes migrating westward across Turkey over the past century, culminating in the 1999 İzmit earthquake near Istanbul.
The East Anatolian Fault had been comparatively quiet during the same period, which created a false sense of security. The 2023 doublet showed that centuries of silence on a major plate boundary doesn’t mean the hazard has gone away. It means the next earthquake will be larger. The fault segments that ruptured had been among the least seismically active sections of the entire East Anatolian Fault Zone in recent decades, storing energy that was ultimately released in one of the deadliest earthquake sequences in Turkey’s modern history.