Science has not yet been able to determine when an earthquake will occur, but studies can determine that a region is at risk of a major earthquake, based on observational and analytical studies that rely on seismic data spanning several years. This is what a German research team did in a study that included the Marmara Fault in Turkey, where they concluded with a very dangerous result, which is that a major earthquake exceeding 7 degrees in the city of Istanbul is now "a matter of time" only.
The Marmara Fault, which was included in the study, is the only part of the North Anatolian Fault system that has not experienced a major earthquake with a magnitude exceeding 7 since 1766. This has attracted the attention of scientists, as historical records indicate that major earthquakes in the region occur on average every 250 years, but approximately 260 years have passed until 2026, and this earthquake has not occurred, which means that this part of the fault has fallen behind its expected date in the seismic cycle.
While scientists at the Helmholtz Centre for Geosciences in Germany were interested in finding out the reasons for this delay, the April 23, 2025 earthquake in the Sea of Marmara raised concerns that a major earthquake was imminent, and more dangerously, that it would be closer to Istanbul, a city of about 18 million people.
The latest earthquake was 6.2 magnitude and was described as the strongest in the region in more than 60 years. When researchers analyzed this earthquake and linked it to a seismic record spanning about 20 years, they discovered an interesting pattern in the study published in the journal Science: moderate-strength earthquakes (greater than 5 magnitude) began in 2011. These earthquakes did not occur randomly, but rather moved gradually from west to east along the fault, and each new earthquake occurred closer to Istanbul than the previous one.
The domino effect began with a 5.1 magnitude earthquake on July 23, 2011, followed by another of the same magnitude on July 25, 2012, then on September 26, 2019 with a magnitude of 5.8, and finally on April 23, 2025 with a magnitude of 6.2, all of which formed a successive series moving eastward towards the "closed section" of the Marmara fault south of Istanbul.
Scientists divide the fault into three sections: the "creeping section," which moves very slowly and continuously, like a door that opens a little each day, so huge amounts of energy do not accumulate in it; the "transitional section," between the creeping and the closed section, where more energy accumulates; and finally, the "closed section," which does not move almost for years or centuries, and is like a rubber band stretched very tightly. When it suddenly breaks, it triggers a large earthquake. This section is located directly south of Istanbul.
Scientists are concerned because recent earthquakes have gradually moved closer to this enclosed section, with the April 23, 2025 earthquake being the most dangerous, as it transferred more stress towards this sector.
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Recent earthquakes have gradually moved closer to this locked section of the fault (Getty)
Two observations that raise concerns
Dr. Patricia Martinez Garzon, from the Helmholtz Centre for Geosciences in Germany, and the lead researcher in the study, told Al Jazeera Net that "the earthquakes that have occurred since 2011 were not randomly distributed along the fault, as might usually happen, but appeared successively in locations that are gradually located to the east, i.e., closer to Istanbul. Analyses of the fault rupture during the earthquakes also showed that the direction of the rupture's spread was also towards the east. Therefore, we are faced with two observations that raise concerns. The first relates to the locations of the earthquakes over decades, and the second relates to the way the rupture spreads within each individual earthquake."
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