Earthquakes in Istanbul in History

Istanbul has held an important position throughout history, both geopolitically and geologically. The city lies in a region close to the North Anatolian Fault Line and is therefore at risk of earthquakes. When Istanbul’s earthquake history is examined, it becomes clear that events have occurred resulting in massive destruction and loss of life.

Byzantine sources record that earthquakes in 557, 869 and 1346 were highly destructive. More detailed records pertain to earthquakes closer to our own time.

This major earthquake is historically referred to as “Kıyamet-i Suğra” (Minor Doomsday). It is known that the quake largely destroyed the city and caused the deaths of thousands of people. The earthquake is estimated to have had a magnitude of approximately 7.4 to 7.7. It is believed to have originated from fault segments north of the Marmara Sea. According to historical records, during the quake cracks formed in the main dome of the Ayasofya, and the city walls suffered extensive damage. A tsunami generated by the quake caused widespread destruction along the Marmara coastlines.

Technical Characteristics of the Earthquake

• Date: 10 September 1509
• Approximate Magnitude: 7.4–7.7 (based on estimates)
• Fault Line: North Anatolian Fault Line
• Affected Area: Marmara Region, especially Istanbul and its surroundings
• Aftershocks: Aftershocks occurred in the region for approximately 45 days after the main quake.

Historical Context

The earthquake occurred during the reign of Ottoman Sultan Bayezid II. This period was one of considerable political and cultural strength for the Ottoman Empire. However, this earthquake deeply shook both the city and its population.

Matrakçı Nasuh described the intensity of the earthquake and its aftermath as follows:

"...Suddenly, on the 25th night of Jumada al-Awwal in the year 914 of the Hijra, while people were asleep, a great earthquake struck Istanbul such that no such quake had occurred since the time of Adam. Ultimately, the Exalted Allah, through the fullness of His power, revealed the form of the Day of Judgment to all creation. From its terror, the universe and space trembled; especially the buildings of Constantinople (Istanbul), which reached heights rivaling the sky, were reduced to rubble. Countless minarets, walls and houses collapsed, and countless people perished beneath the debris.

^{(Source, 1509 Istanbul Earthquake, AI)}

Effects and Damage

• Loss of Life and Injuries: Sources indicate that approximately 10,000 to 13,000 people lost their lives and more than 10,000 were injured.
• Structural Damage: A large part of the city was destroyed. The city walls, homes, mosques, madrasas and other structures suffered severe damage. The Ayasofya sustained serious damage, with cracks appearing in its dome.
• Tsunami: Tsunami waves generated after the earthquake caused flooding along the Marmara coastlines, increasing the destruction.

Social and Economic Effects

In the aftermath of the earthquake, a large-scale migration wave occurred. Food shortages, epidemics and security problems emerged in the city. Economic activity nearly came to a halt, and tradespeople and merchants suffered major losses.

Geological Context

The 1509 earthquake resulted from the rupture of one of the segments of the North Anatolian Fault Line (NAF) beneath the Marmara Sea. This fault lies along the boundary between the Eurasian Plate and the Anatolian Plate and is a strike-slip fault system.

The earthquake of 1766 is recorded as one of the most destructive in Istanbul’s history. It caused heavy damage on both the European and Anatolian sides of the city. In the aftermath, extensive restoration work was carried out on historical structures such as Topkapı Palace and Ayasofya. According to records from Ottoman archives, economic losses caused by the earthquake were addressed through tax amnesties and state aid.

Technical Characteristics of the Earthquake

• Date: 22 May 1766
• Approximate Magnitude: 7.1–7.5 (based on estimates)
• Epicenter: Northeastern coast of the Marmara Sea
• Fault Line: North Anatolian Fault Line
• Aftershocks: Aftershocks were recorded for several months after the main quake.

Historical and Social Context

The 1766 Istanbul earthquake occurred during the reign of Ottoman Sultan Mustafa III. This was a period marked by reform efforts and modernization initiatives within the Ottoman Empire. However, the earthquake negatively affected Istanbul’s political and economic structures, hindering recovery efforts.

^{(Source, gdh.digital, 22 May 1766 earthquake)}

Effects and Damage

• Loss of Life and Injuries: It is estimated that between 4,000 and 6,000 people lost their lives. The number of injured was very high, with many affected by shelter and health problems following the quake.
• Structural Damage: Many important structures in Istanbul suffered severe damage. Topkapı Palace, Fatih Mosque, Yedikule, Eğrikapı, Edirnekapı and the city walls were heavily damaged. Damage also occurred in Galata, Pera, the Grand Bazaar, Ayasofya and other mosques.
• Tsunami: Tsunami waves generated after the earthquake caused additional destruction along coastal areas.

Social and Economic Effects

Trade and the economy suffered greatly, forcing many tradespeople to close their shops. A large migration wave occurred after the earthquake, with migrants from rural areas contributing to the city’s reconstruction. The Ottoman State implemented measures such as tax amnesties to compensate for public losses.

Geological Context

The Marmara Sea is a pull-apart basin formed by the North Anatolian Fault Line. The 1766 earthquake resulted from the rupture of a segment of this fault beneath the Marmara Sea, causing widespread destruction in Istanbul and its vicinity.

The earthquake of 1894 is remembered as one of the most destructive to strike Istanbul during the Ottoman Empire. It holds a significant place in history due to both its physical destruction and its social and economic consequences.

Technical Characteristics of the Earthquake

• Date: 10 July 1894
• Approximate Magnitude: 7.0–7.3 (based on estimates)
• Epicenter: East of the Marmara Sea, near the Princes’ Islands
• Fault Line: North Anatolian Fault Line

Historical and Social Context

The 1894 earthquake, recorded during the Ottoman period, occurred under the reign of Sultan Abdülhamid II. Following the quake, at the Sultan’s instruction, construction of fire-resistant and more robust buildings began in Istanbul.

^{(Repair of arches in the Grand Bazaar after the 1894 earthquake, year 1896)}

Effects and Damage

• Loss of Life and Injuries: It is estimated that between 1,000 and 5,000 people lost their lives. The number of injured is described in the thousands.
• Structural Damage: Istanbul’s key structures suffered severe damage. Cracks appeared in the dome of the Ayasofya Mosque and its walls were damaged. Cracks formed in Istanbul’s city walls, and many hans, mosques and bazaars collapsed. Structures along the Marmara coast were destroyed by the tsunami. Kumkapı, Galata and Üsküdar areas were severely affected. In neighborhoods with wooden houses, major fires broke out, compounding the damage.
• Tsunami: The earthquake in the Marmara Sea generated a tsunami that caused flooding along coastal regions.

Social and Economic Effects

Markets and bazaars suffered major destruction, bringing commercial life to a standstill. The poor were the most affected group. Temporary shelter shortages and food scarcity emerged. The Ottoman State mobilized to assist victims and organized large-scale relief campaigns.

Geological Context

The Marmara Sea lies under the influence of the North Anatolian Fault Line, whose activity is the primary cause of earthquakes in the region. The 1894 Istanbul earthquake once again highlighted the city’s seismic risk and underscored the importance of constructing buildings capable of withstanding earthquakes.

The 1999 earthquake released a large portion of the accumulated energy along the Marmara segment of the North Anatolian Fault Line, but also increased the risk of a future major earthquake threatening Istanbul.

Technical Characteristics of the Earthquake

• Date: 17 August 1999
• Moment Magnitude (Mw): 7.4
• Local Magnitude (ML): 7.8
• Time: 03:02
• Duration: 45 seconds
• Epicenter: Gölcük, Kocaeli (Türkiye)
• Coordinates: 40.746°N, 29.864°E
• Fault Line: North Anatolian Fault Line
• Focal Depth: 17 km
• Fault Rupture Length: 150 km
• Fault Rupture Velocity: 3.5 km/hour
• Maximum Surface Displacement: 5.5 m

^{(Source, Anadolu Agency, 17 August 1999 earthquake)}

Effects and Damage

• Loss of Life and Injuries: According to official reports, 17,480 people died and 23,781 were injured. A 2010 parliamentary research report revised these figures to 18,373 dead and 48,901 injured.
• Material Damage: The earthquake caused damage to 285,211 homes and 42,902 commercial premises, leaving approximately 200,000 people homeless.
• Affected Areas: The earthquake was strongly felt across a wide area of the Marmara Region, causing major destruction in Kocaeli, Sakarya, Yalova, Istanbul, Bolu, Bursa and Eskişehir.

Social and Economic Effects

A major humanitarian crisis followed the earthquake, with search and rescue operations lasting for days. National and international aid organizations provided support to meet the shelter, nutrition and health needs of earthquake victims.

Geological Context

The earthquake occurred along the North Anatolian Fault Line, which forms the boundary between the Eurasian and Anatolian plates and is a right-lateral strike-slip fault. The quake generated a surface rupture approximately 150 km in length.

^{(Source, AFAD)}

Istanbul, located along the northern branch of the North Anatolian Fault Line (NAF), is a metropolis with high seismic risk. Having experienced many major earthquakes throughout history, the city may face a new major quake in the coming years, as warned by scientists.

• Expected Major Earthquake: Estimated magnitude of 7.0–7.6.
• Estimated Probability: A major earthquake is expected with up to a 50% probability within the next 30 years. (2025)

• Marmara Sea Segment: The unruptured portion of the North Anatolian Fault beneath the sea, located 20–30 km south of Istanbul, poses a major risk.
• Stress Accumulation: Tension has continued to accumulate in the Marmara Region since the 1999 Gölcük earthquake.
• Geological Studies: Boğaziçi University’s Kandilli Observatory and TÜBİTAK continue monitoring seafloor surveys and fault movements.

• Earthquake-Resistant Buildings: Structures built after 2000 are more robust, but 60% of buildings constructed before 1999 remain at risk.
• Urban Transformation Projects: Progress is slow, but districts such as Avcılar, Zeytinburnu, Fatih, Küçükçekmece and Bahçelievler are in high-risk categories.
• Infrastructure Projects: New metro lines and bridges are being constructed in compliance with earthquake regulations.

• Estimated Death and Injury Toll: Over 30,000 fatalities are possible.
• Building Collapses: Nearly 50,000 buildings could be completely destroyed, and close to 500,000 could suffer severe damage.
• Economic Loss: The earthquake could inflict over $100 billion in damage to Istanbul’s economy.

• AFAD and Kandilli Observatory are developing early warning systems.
• The Istanbul Earthquake Master Plan, prepared by the Istanbul Metropolitan Municipality, has identified high-risk zones and aims to accelerate urban transformation.
• Earthquake drills and public awareness campaigns are being conducted.

• Individual Measures: Prepare an emergency kit and develop an evacuation plan.
• Building Strengthening: Retrofit older buildings to make them earthquake-resistant.
• Local Government and State-Level Measures: Accelerate urban transformation, expand gathering areas and reinforce infrastructure.

Istanbul has been shaken by major earthquakes throughout history and remains under a significant seismic threat today. Scientists emphasize that a major earthquake beneath the Marmara Sea is inevitable and that preparedness is essential. The city can minimize the impact of this disaster by taking necessary measures, but greater awareness and preparedness at both individual and institutional levels are required.