“Pancake collapse” of an apartment building following the Mw = 7.6 Izmit earthquake, which shook western Turkey in 1999. Credit: Mohi Kumar

Over the past century, a string of devastating earthquakes rocked Turkey, killing more than 80,000 people. Two of the largest events, the 1939 Erzincan earthquake and the 1999 İzmit and Düzce earthquake pair, killed 32,700 and 18,000 people, respectively. According to new research by Ergintav et al., the most significant seismic hazard—potentially up to a magnitude 7.2 event—is most likely posed by a section of fault centered just a few dozen kilometers south of Istanbul, home to more than 14 million people.

The Erzincan, İzmit, and Düzce earthquakes were just three in a string of more than a dozen major ruptures of the North Anatolian Fault, a major seismic system that runs east–west across northern Turkey. As previous research has shown, over the past century, the epicenters of major earthquakes on the North Anatolian Fault have been steadily creeping westward.

Using 20 years of GPS ground motion observations, the authors modeled the accumulation of seismic strain in the North Anatolian fault system. Their calculations give an indication of where the next big earthquake is likely to hit. The authors suggest that a stretch of the fault system near the Prince Islands, an archipelago in the Sea of Marmara just south of Istanbul, is the most likely candidate. They found that the region is seismically locked—it should be slipping about 10 to 15 millimeters each year, but it is not.

Previously, researchers suggested that a stretch of the fault system much farther west, out in the Sea of Marmara, was the most likely candidate for an impending earthquake. The authors’ observations suggest that this region is not accumulating stress. The authors’ research, then, moves the most likely location for a major earthquake closer to Istanbul.

The last time the fault section near the Prince Islands ruptured, in 1766, it caused massive damage to Istanbul. (Geophysical Research Letters, doi:10.1002/2014GL060985, 2014)

—Colin Schultz, Freelance Writer

Citation: Schultz, C. (2015), Seismic stress modeling puts Istanbul in the crosshairs, Eos, 96, doi:10.1029/2015EO025213. Published on 3 March 2015.

Text © 2015. The authors. CC BY-NC 3.0
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