Research conducted over the years has shown that Istanbul was shaken by more than 500 great earthquakes since the day it was founded. While some of them were earthquakes that occurred due to the fault lines around the city and caused heavy damage, many of them were caused by fault lines in the Thrace and İzmit-Düzce regions and caused less destruction
Earthquakes in Byzantine period
Twenty years after Roman Emperor Constantine I, known as Constantine the Great, founded Constantinople (modern day Istanbul), an earthquake occurred east of the city in 342, but it did not cause much damage.
On Aug. 24, 358, the earthquake which brought down İzmit affected the ancient city of Constantinople as well. Earthquakes which hit Constantinople in 402,412,417,423,437 and 442 caused considerable damage to the city although not as much as the earthquake in 358. The city continued to be shaken in 450, 477, 487, 525 and 533, as well.
The quake that hit the city on Aug. 16, 542 was massive; many houses, city walls and statues were demolished and thousands of people died. The damage caused by an earthquake on May 7, 558 following the earthquakes of 546 and 557 was substantial. The dome of the Hagia Sophia collapsed and thousands of houses collapsed. After the earthquakes of 583 and 611, Constantinople was earthquake-free for a long time.
Nearly 130 years later, on Oct. 26, 740, Constantinople was hit by a great earthquake. After which the quakes continued in 780, 790, 860, 866, 869, 989 and 1010. The city was also destroyed by two earthquakes on Aug. 13, 1032 and March 6, 1033 in succession. The earthquakes in 1042 and 1064 followed them. On March 1, 1202, an earthquake occurred in the city which caused the floor in front of the Byzantine Emperor's bed to crack open and an agha of the House of Felicity died by falling into the hole.
In the massive earthquake that occurred on March 11, 1231, the city and city walls were damaged. On June 1, 1296, seven years after the earthquake in 1289, which was not so massive, a big earthquake hit Istanbul in the night.
Historians write that Istanbul was leveled to the ground in this earthquake. Houses, palaces, churches and city walls were demolished. Floods occurred, and aftershocks continued for two months. The Byzantines lived through some scary days. Then Istanbul was hit by two successive earthquakes in January 1303. As the quake happened during the appointment of Athanasius I as the patriarch for the second time, word started going around by the religious men of the period who said that the patriarch did not have a benediction.
The earthquake of 1332 destroyed many houses and churches together with statues. The earthquake on Oct. 18, 1343 was also so massive. The city walls and Hagia Sophia were damaged. While the Byzantines were happy that the Ottoman Empire was defeated by the Timurid Empire in 1402, an earthquake in Constantinople interrupted their joy. It is asserted that there was a tsunami caused by the earthquake of 1419. The last earthquake in Istanbul during the Byzantine Period was in 1437.
Earthquakes in Ottoman period
The first big earthquake in Istanbul when it came under the rule of the Ottoman Empire took place on Dec. 18, 1488. While the dome of the Fatih Mosque was demolished, different regions of the city were damaged as well. On Sept. 10, 1509, Istanbul was shaken by a big quake at 4 a.m. Before the people understood what was happening, the whole city was destroyed. According to experts, the earthquake in 1509 in Istanbul was the biggest one in the Eastern Mediterranean after the year 1000. It was felt in the area from Bolu province to Edirne province. It was called "Little Doomsday."
Another earthquake hit the city on the night of May 10, 1556. The Fatih Mosque, Hagia Sophia and city walls were damaged. After this earthquake, Istanbul did not experience an earthquake for 90 years.
Then on June 28, 1648, people in İzmit and Istanbul woke up with a shake in the morning. However, the epicenter was far so it did not damage Istanbul much. The city was shaken again by a quake on July 11, 1690. As it was not so massive, the damage in the city was not considerable. City walls, some wooden houses were demolished along with the Fatih Mosque. The earthquake that occurred during the morning prayers on May 25, 1719 was massive. The destruction area of the earthquake started from Düzce, reaching İzmit, Sapanca, Orhangazi, Karamürsel and Yalova. Yalova was hugely damaged by this quake.
The earthquake of May 25, 1719 damaged Istanbul although not as much as İzmit. The city walls were considerably damaged. Some mosques and palaces were ruined. Forty mosques and 27 bastions were demolished. On July 30, 1752, an earthquake occurred and affected the region all the way till Bulgaria. While Edirne was highly damaged, Istanbul was not affected much by this shake. Then an earthquake hit Istanbul on the night of Sept. 2, 1754 but it did not cause much damage as it was not so massive. The dome of the Fatih and Bayezid Mosques were destroyed together with one of the bastions of Yedikule. The shake principally affected İzmit and its surroundings.
Last big earthquakes
The second biggest earthquake in Istanbul, under the dominance of the Ottoman Empire, occurred on May 22, 1766. The shake, which started half an hour after sunrise on that day, was the third day of Qurban Bayram (or Eid al-Adha in Arabic). Scary noises were heard during the quake, and a two-minute-long shake followed them. Then, a less intense quake hit the city for four minutes. The aftershocks of this quake continued for eight minutes. On Aug. 5, another shake occurred. After the 1766 quake, Istanbul went for some years without any earthquakes.
Even though the earthquake in 1855 demolished Bursa province and affected Istanbul, it did not destroy the city much.
Istanbul was hit by a massive earthquake on July 10, 1894. This quake, which continued for 18 seconds was felt in three waves. It affected Adapazarı, İzmit, Gebze, Kartal, the Prince's Islands, Üsküdar, İstanbul, Büyükçekmece, Küçükçekmece, Çatalca, a part of the Marmara Sea, Bozburun, Yalova, Karamürsel and Sapanca.
The last big earthquake to affect Istanbul during the Ottoman period was the one in Şarköy-Mürefte, recorded at a magnitude of 7.3 on Aug. 9, 1912. It considerably damaged the south of Edirne destroying chimneys, telegraph poles and walls.