Abstract: Byzantion (stanbul), Perinthos (Marmara Erelisi), and Cyzikos (Belkıs) were the most important portsof the Marmara Sea in ancient times. While Byzantion was an estuary, Perinthos and Cyzikos weretombolo type ports. Although Byzantion has continued to develop since its foundation, Perinthos has lostits importance as a port in the Marmara Sea, and Cyzikos has been abandoned and turned in the Belkıs ruins. Another point shared by Perinthos and Cyzikos, which were turned in ports after theFlandrian transgression, is that they are very close to branches of the North Anatolian Fault. Perinthosis located on the northern shoreline of the Marmara Sea, 90 km west of the Bosphorus. The northernbranch of the North Anatolian Fault crosses just a few km to the south of the town. Earthquakes,tectonic uplift, tsunamis, offshore landslides and floods have had natural effects on the foundation anddevelopment of this ancient city. Although Perinthos is on a seismically active area, there areinsufficient historical records of faulting events with the exception of those which heavily damagedIstanbul. The oldest earthquake record is a December 427 BC event; the intensity of the Geliboluearthquake was VIII in 282 BC; but the effects of the 90 BC Saros and 93 BC Canakkale earthquakesare unknown for Perinthos. There are historical records of repairs on the City walls in the 2nd and 3rdcenturies.. The damage to these city walls might have happened after the 10 November 117 Kapıda Peninsula, 138 Çanakkale-Bandırma, 160 Çanakkale and 3 May 170 Marmara Sea earthquakes.Perinthos was still alive at the beginning of Byzantine era. The residents of the town asked the EmperorTheododius the Second for the restoration of aqueducts which were damaged by the 430 Istanbulearthquake (I=VIII). While there were no significant known effects of the 478 Çanakkale and 484Gelibolu events, damage from the 6 September 543, 553 Canakkale, 557 Silivri and 558 Istanbul oneswere fixed immediately. The name of the town changed to Herakleia in this period. Aqueducts and citywalls were repaired again in Justinian`s times (527-568). Other earthquakes that effected the townoccurred in 715, 740 (Marmara Sea and Thrace shores), 760 (Istanbul and Thrace), 860 (Marmara),989 (Marmara), 23 September 1063/1064 (Bandırma, Cyzikos, İznik, Mürefte, Istanbul), 1296 (Istanbul,Marmara), 1343 (Erei-Ganos), 14 October 1344 (Gelibolu, Thrace shores, Istanbul Marmara Island),1 March 1354 (Gelibolu, Marmara northern shores, Thrace), September-November 1437 (Istanbul andGelibolu).