Scientists warn that conditions for a major earthquake are currently present beneath Istanbul, Turkey, home to 18 million residents. The country is situated at the convergence of multiple tectonic plates, with significant fault lines such as the North Anatolian Fault and the East Anatolian Fault. Recent seismic activity includes a 6.2 magnitude earthquake in April 2025, the strongest in 60 years, along the Marmara Sea fault segment near Istanbul, which remains locked and has not experienced a major quake since 1766. This segment is overdue for a significant rupture, with the average recurrence cycle estimated at 250 years, indicating a growing risk of a devastating earthquake. Paleoseismological studies reveal that large earthquakes tend to migrate westward along the fault, with the segment under the Marmara Sea, directly south of Istanbul, being the most critical. Current research shows that while larger magnitude earthquakes are moving west, smaller ones of magnitude 5+ have been shifting eastward over the past 15 years, leaving the southern part of the Marmara segment locked and vulnerable. Experts emphasize the need for enhanced real-time monitoring, including installing new seismic stations, to better predict and prepare for an imminent major quake. The potential for a magnitude 6 or higher earthquake on this locked segment could trigger a larger, more destructive event, posing a severe threat to Istanbul and surrounding regions.