  | |
| Local date | 5 August 1766 |
|---|---|
| Magnitude | 7.4–7.6 Mw |
| Epicenter | 40°36′N 27°00′E / 40.6°N 27°E |
| Fault | North Anatolian Fault |
| Areas affected | Ottoman Empire |
| Max. intensity | MMI X (Extreme) |
| Tsunami | None |
| Casualties | >5,000 fatalities |
The 1766 Marmara earthquake occurred on 5 August; the second major earthquake to strike the Sea of Marmara region of present-day Turkey that same year. Estimates of the earthquake's moment magnitude (Mw ) range between 7.4 and 7.6. The earthquake was caused by strike-slip movement along a segment of the North Anatolian Fault. There was further damage and casualties in the Sea of Marmara area which had been affected by another major earthquake in May 1766. The worst affected areas were Tekirdağ and Gelibolu.