Engineering summary
A 2024 study by Kalkan and Gulkan puts Istanbul's western shoreline at highest earthquake risk, with median PGA of 0.65 g in Bakırköy and Adalar under multi-fault Marmara rupture scenarios.
In short: Istanbul earthquake risk is highest in the districts nearest the North Anatolian Fault under the Marmara Sea, particularly Adalar, Bakırköy, Avcılar and Zeytinburnu on the western shoreline. A 2024 study by Kalkan and Gulkan estimates median spectral acceleration at 0.3 s approaching 1 g there and median peak ground acceleration of 0.65 g in Bakırköy and Adalar for combined rupture of the Off-Tekirdağ, Mid-Marmara and Islands faults.
Istanbul, straddling two continents, is not just a city of unparalleled historical and cultural wealth but also one that lives in the shadow of a significant seismic threat. The North Anatolian Fault (NAF), a major source of earthquakes in the region, skirts to the south and east of this vibrant metropolis, placing it at a heightened risk of seismic activity. But in a city so vast, the question arises: which district of Istanbul will bear the brunt of such an inevitable shake?
The sequence of westerly propagating ten large (M>6.7) earthquakes on the North Anatolian Fault Zone and the seismic gap in the Sea of Marmara close to Istanbul is an indication of a large earthquake.
The Epicenter of Concern: The Riskiest Districts
Historical data and seismic studies indicate that the districts closest to the North Anatolian Fault zone beneath the Marmara Sea, especially those on the city’s European side, are more vulnerable. Our most recent study (Kalkan and Gulkan, 2024) indicates that Istanbul’s western shoreline faces heightened risk, with median spectral accelerations at 0.3 s approaching 1 g, signifying intense shaking potential. Among these, Adalar, Bakırköy, Avcılar, and Zeytinburnu stand out as areas that might experience the most intense shaking. These districts, with their dense populations and structures, many of which were built before modern seismic standards were implemented, could face significant impacts in the event of a major earthquake.
The figure above shows close-up to peak ground acceleration (PGA) estimates for the Istanbul metropolitan area considering six earthquake scenarios. The median computed PGA is 0.65 g along the shoreline to the west of Istanbul (Bakırkoy district) and at Marmara Islands (Adalar district) as a result of multiple rupturing of Off-Tekirdağ, Mid-Marmara, and Islands faults.
The Science of Shaking: Understanding the Risk
Seismic risk is not only about proximity to the fault line but also about the ground beneath. Areas built on softer, sedimentary layers, such as parts of Avcilar, Atakoy, and Bakırköy amplify seismic waves, leading to more intense shaking compared to those on more solid rock. This geological variability across Istanbul means that the impact of an earthquake can differ dramatically, even within short distances.
Preparedness: The Key to Resilience
While the threat is significant, the focus now is on resilience and preparedness. Istanbul’s government and various organizations are working tirelessly to retrofit vulnerable buildings, improve emergency response systems, and educate the public about earthquake preparedness. Efforts are particularly concentrated in the high-risk districts, aiming to minimize the impact when the inevitable occurs.
Conclusion: A City Bracing for Its Future
As Istanbul faces its seismic future, understanding the areas at greatest risk is crucial for safeguarding its residents and heritage. While many districts along its shoreline may be more vulnerable, city-wide efforts to enhance resilience are a testament to Istanbul’s determination to protect its people and preserve its legacy against the forces of nature.
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Are you from Istanbul or have experiences related to earthquakes in the city? Reach us at info@quakelogic.net
Key Takeaways
- Ten westward-propagating M>6.7 earthquakes on the North Anatolian Fault and a Marmara Sea seismic gap point to a coming large event near Istanbul.
- Adalar, Bakırköy, Avcılar and Zeytinburnu are expected to shake most; many buildings there predate modern seismic codes.
- Kalkan and Gulkan (2024) report median 0.3 s spectral accelerations approaching 1 g along Istanbul's western shoreline.
- Across six scenarios, median PGA reaches 0.65 g in Bakırköy and Adalar from joint rupture of the Off-Tekirdağ, Mid-Marmara and Islands faults.
- Soft sedimentary ground in Avcılar, Ataköy and Bakırköy amplifies shaking compared with districts on rock.
Frequently Asked Questions
The Istanbul districts most at risk are those closest to the North Anatolian Fault beneath the Marmara Sea, especially on the European side: Adalar, Bakırköy, Avcılar and Zeytinburnu. These areas combine proximity to the fault, soft sedimentary ground that amplifies shaking, dense populations and many buildings constructed before modern seismic standards, so they are expected to experience the most intense shaking and damage.
Scenario modeling by Kalkan and Gulkan (2024) shows median spectral acceleration at 0.3 s approaching 1 g along Istanbul's western shoreline. For peak ground acceleration, the median estimate across six earthquake scenarios reaches 0.65 g along the shoreline west of the city in Bakırköy and on the Marmara Islands in Adalar, driven by a multi-segment rupture of the Off-Tekirdağ, Mid-Marmara and Islands faults.
A sequence of ten large earthquakes with magnitude above 6.7 has propagated westward along the North Anatolian Fault Zone, loading the next segment in line. The section beneath the Sea of Marmara close to Istanbul has not ruptured recently and forms a seismic gap. That unbroken, stressed segment is why seismologists regard a large Marmara earthquake as inevitable rather than merely possible.
Local geology controls how much seismic waves are amplified. Districts built on soft sedimentary layers, such as parts of Avcılar, Ataköy and Bakırköy, trap and amplify seismic energy, producing stronger and longer shaking than districts on firm rock at a similar distance from the fault. This site effect means shaking intensity can change dramatically over a few kilometers within Istanbul.
Istanbul's government and partner organizations are retrofitting vulnerable buildings, improving emergency response systems and running public earthquake-preparedness education, with efforts concentrated in the high-risk shoreline districts. Identifying which districts will shake most, using scenario-based ground motion studies, lets authorities prioritize retrofit budgets and response planning where the combination of hazard, soft soil and older building stock is worst.
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Topic cluster
Related engineering knowledge areas
- Earthquake EngineeringSeismic hazard, ground motion, structural response, fragility, and resilience guidance.
- Structural Health MonitoringMonitoring for bridges, buildings, dams, tunnels, industrial facilities, and resilient infrastructure.
- Earthquake Early WarningOn-site detection, alerting workflows, seismic switches, and critical infrastructure warning systems.
- Infrasound MonitoringLow-frequency acoustic sensing for environmental noise, blast, UAV, volcano, and defense applications.
Definitions and references
Terms, standards, and source cues
- seismic hazard: related to Earthquake Engineering in this QuakeLogic knowledge cluster.
- ground motion: related to Earthquake Engineering in this QuakeLogic knowledge cluster.
- SHM: related to Structural Health Monitoring in this QuakeLogic knowledge cluster.
- damage detection: related to Structural Health Monitoring in this QuakeLogic knowledge cluster.
- earthquake early warning: related to Earthquake Early Warning in this QuakeLogic knowledge cluster.
- seismic switch: related to Earthquake Early Warning in this QuakeLogic knowledge cluster.
- infrasound sensors: related to Infrasound Monitoring in this QuakeLogic knowledge cluster.
- low-frequency noise: related to Infrasound Monitoring in this QuakeLogic knowledge cluster.
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