Centered in the Sea of Marmara, 45 km southeast of Tekirdag at a shallow 8-10 km depth; felt strongly in Istanbul (MMI V-VI shaking) and as far as Bursa, Yalova, and Balikesir, with no major damage reported yet.
Thousands evacuated buildings and schools; crowds gathered in parks amid aftershocks (up to 4.0); AFAD and governors' offices report no casualties, but emergency services on high alert with shelters activated.
Latest in a series of tremors (e.g., April's 6.2 quake injured 236 via panic); highlights Istanbul's high-risk fault zone, with experts urging preparedness for a potential 7+ event.