Turkey: Magnitude 5 Earthquake in the Marmara Sea

An earthquake struck Turkey on Thursday afternoon, October 2, 2025, in the Marmara Sea near Istanbul. According to an emergency announcement by Turkey’s Disaster and Emergency Management Authority (AFAD), a magnitude 5.0 quake hit offshore in the Marmara Sea, with a focal depth of 6.71 kilometers. The tremor was strongly felt in Istanbul and surrounding provinces. The Kandilli Institute recorded the quake at magnitude 5.3. So far, no damage has been reported in Istanbul, but authorities warn residents to remain cautious and avoid buildings that may have sustained structural harm. Professor Dr. Sener Ozturkmezsoy spoke to CNN Turk, stating, “This region could experience similar seismic activity. The quake did not occur off Tekirdag, but at the western end of the Silivri basin.” He added, “This is half of the scenario I mentioned on April 23.” Ozturkmezsoy reminded viewers that during the April 23 magnitude 6.2 quake in Kumulca, only part of the fault ruptured, while a 10–15 kilometer segment within the Silivri basin remains unactivated. “On April 23, I warned that the quake occurred along the fault between Silivri and Buyukcekmece, measuring 6.2. However, the section extending underwater from the Silivri basin to Ereğli had not yet ruptured. Now, fracturing is occurring there. That means only half the expected shaking has happened—the other half has yet to come,” he emphasized.