Geophysicist Says Marmara’s Hot Mantle Weakens Undersea Faults
istanbul earthquake
A groundbreaking seismic theory from Geophysicist Prof. Dr. Osman Bektaş sheds new light on the Marmara Sea earthquake risk, challenging popular assumptions about where the most devastating tremors may strike.
According to Bektaş, the geophysical structure beneath the Marmara Sea reveals a distinct pattern: undersea faults tend to produce earthquakes below magnitude 7, while land-based faults, particularly those locked in cooler, denser crust, are capable of triggering destructive earthquakes above magnitude 7—as seen in the 1999 İzmit Earthquake.
The Mantle Clue Beneath the Marmara Sea
The crux of Bektaş’s theory lies in the mantle layer’s proximity to the surface beneath the Marmara Sea. This hot, rising mantle, shown in red on the geophysical map he shared, has thinned and weakened the lithosphere—the rigid outer shell of the Earth—beneath the sea.
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In these “hot and thin crust” zones (around 10 km thick), the fault lines are more flexible and prone to frequent, smaller quakes due to a phenomenon known as creep, where energy is released gradually.
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In contrast, “cold and thick crust” regions on land, such as İzmit, are about 17 km thick and lock seismic energy for decades, leading to more powerful and sudden earthquakes.
Explaining Past Earthquakes with Crust Differences
Bektaş emphasizes that historical earthquake data supports his model.
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The 1999 İzmit Earthquake (M7.4) occurred in a land-based, cold crust zone—shown in blue—where seismic energy had built up over time.
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By contrast, undersea events like the 1963 Adalar Earthquake (M6.3) and 1935 Marmara Island Earthquake (M6.4) took place in the hot crust zone, staying below magnitude 7.
New Outlook on Earthquake Risk in Istanbul
Bektaş’s theory doesn’t eliminate the risk of a major earthquake in the Marmara region but offers a more nuanced understanding of where and how large future quakes might be. It also proposes a fresh lens for earthquake preparedness and disaster risk management in Istanbul and surrounding areas.
His findings add a scientific framework to explain why quakes under the sea tend to be less severe and why land-based faults remain a greater threat, supporting a more informed approach to seismic risk.
