Earthquakes in Istanbul in History

Istanbul has held a strategically significant position throughout history, both geopolitically and geologically, important. Due to its location along the North Anatolian Fault Line, City, it is at risk. When examining Istanbul’s earthquake history, events resulting in massive destruction and can losses are evident.

Byzantine sources record that the earthquakes of 557, 869, and 1346 were highly destructive. More detailed records pertain to earthquakes closer to the present day.

The 1509 Earthquake: Kıyamet-i Suğra

This major earthquake has been historically referred to as “Kıyamet-i Suğra” (Minor Judgment Day). It is known that the quake largely destroyed the city and caused the deaths of thousands. The earthquake is estimated to have had a magnitude of approximately 7.4–7.7. It is believed to have originated from one of the fault segments north of Sea of Marmara. According to Historical records, during the quake, cracks formed in the great dome of Hagia Sophia, and the city walls suffered extensive damage. Tsunami caused significant damage along the Marmara coast.

Technical Characteristics of the Earthquake

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

Historical Context

The earthquake occurred during the reign of Ottoman Sultan Bayezid II. This period was a period of considerable political and cultural strength for the Ottoman Empire. However, the 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 night of the 25th of Jumada al-Awwal in the year 914 of the Hijra, while people were asleep, a great earthquake struck Istanbul such that none had occurred since the fall of Adam. In the end, the Lord, in His infinite power, revealed the form of Judgment Day to all creation. The universe trembled in fear of His dread; 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 ruins.”

(Source, 1509 Istanbul Earthquake, AI)

Effects and Damage

• Human Loss and Injuries: According to sources, approximately 10,000 to 13,000 people lost their lives and more than 10,000 were injured.
• Structural Damage: A large portion of the city was destroyed. Istanbul’s walls, houses, mosques, madrasas, and other structures suffered severe damage. Hagia Sophia sustained serious damage, with cracks appearing in its dome.
• Tsunami: Tsunami waves generated in the Sea of Marmara after the earthquake caused flooding along coastal areas and increased destruction.

Social and Economic Effects

A widespread migration wave followed the earthquake. Food shortages, epidemics, and security issues head emerged. Economic activity nearly came to a halt, 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 Sea of Marmara. This fault lies along the boundary between the Eurasian Plate and the Anatolian Plate and is a strike-slip fault system.

The 1766 Earthquake

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 Hagia Sophia. According to records from Ottoman archives, economic losses caused by the earthquake were mitigated through tax amnesties and state aid.

Technical Characteristics of the Earthquake

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

Historical and Social Context

The 1766 Istanbul earthquake occurred during the reign of Ottoman Sultan III. Mustafa. This period was a time when the Ottoman Empire was noted for its reform efforts and modernization initiatives. However, this earthquake negatively affected Istanbul’s political and economic structure, hindering recovery efforts.

(Source, gdh.digital, 22 May 1766 earthquake)

Effects and Damage

• Human Loss and Injuries: It is estimated that between 4,000 and 6,000 people lost their lives. The number of injured was very high, with a large portion affected by post-earthquake shelter and health issues.
• Structural Damage: Many important structures in Istanbul suffered severe damage. Topkapı Palace, Fatih Mosque, Yedikule, Eğrikapı, Edirnekapı, and the city walls sustained heavy damage. Damage also occurred in Galata, Pera, the Grand Bazaar, Hagia Sophia, and other mosques.
• Tsunami: Tsunami waves generated in the Sea of Marmara caused additional destruction along coastal areas.

Social and Economic Effects

Trade and the economy suffered extensive damage, forcing many merchants to close their shops. A large wave of migration followed the earthquake. Migrants from rural areas contributed significantly to the city’s reconstruction. The Ottoman State implemented measures such as tax amnesties to compensate for public losses.

Geological Context

The Sea of Marmara 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 Sea of Marmara. The rupture caused extensive destruction in Istanbul and its surroundings.

The 1894 Istanbul Earthquake: “Büyük Hareket-i Arz”

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

Technical Characteristics of the Earthquake

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

Historical and Social Context

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

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

Effects and Damage

• Human Loss and Injuries: It is estimated that between 1,000 and 5,000 people lost their lives. The number of injured is expressed in the thousands.
• Structural Damage: Istanbul’s key structures suffered severe damage. Cracks appeared in the dome of Hagia Sophia 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. Particularly Kumkapı, Galata, and Üsküdar suffered serious damage. Neighborhoods with wooden houses experienced major fires, which amplified the destruction.
• Tsunami: The earthquake in the Sea of Marmara triggered a tsunami that caused flooding along coastal areas.

Social and Economic Effects

Significant destruction occurred in markets and market areas, 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 Sea of Marmara lies within the influence of the North Anatolian Fault Line, whose activity is the main cause of earthquakes in the region. The 1894 Istanbul earthquake once again highlighted the city’s seismic vulnerability and emphasized the importance of constructing earthquake-resistant buildings.

The 1999 Kocaeli (Gölcük) Earthquake

The 1999 earthquake released a large portion of the accumulated energy along the Marmara segment of the North Anatolian Fault Line, yet it 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 Slip: 5.5 m

(Source, Anadolu Agency, 17 August 1999 earthquake)

Effects and Damage

• Human Loss and Injuries: According to official reports, 17,480 people lost their lives 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 felt across a wide area of the Marmara Region and caused 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. This fault forms the boundary between the Eurasia and Anatolian plates and is a left-lateral strike-slip fault. The earthquake generated a surface rupture approximately 150 km in length.

(Source, AFAD)

Contemporary Perspective

Istanbul’s Seismic Risk Status

Istanbul, located along the northern branch of the North Anatolian Fault Line (NAF), is a metropolis with high seismic risk. The city, having experienced numerous major earthquakes throughout history, may face a new major earthquake in the coming years, as science have warned.

• 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)

Recent Research and Fault Line Status

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

Istanbul’s Structural Resilience

• Earthquake-Resistant Buildings: While structures built after 2000 are more robust, 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.

Potential Earthquake Scenario and Expected Outcomes

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

Measures and Preparedness Efforts

• AFAD and Kandilli Observatory are developing early warning systems.
• The Earthquake Master Plan (prepared by Istanbul Metropolitan Municipality) identifies high-risk zones and aims to accelerate urban transformation.
• Campaigns are underway to conduct earthquake drills and raise public awareness.

Recommendations for Istanbul

• Individual Measures: Prepare an emergency kit and develop an evacuation plan.
• Building Strengthening: Retrofit older buildings to make them earthquake-resistant.
• Local and National Government 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 in the Sea of Marmara is inevitable and that preparedness is essential. The city can minimize the impact of this disaster by taking necessary measures. However, greater awareness and preparedness at both individual and institutional levels are required.