Devastating earthquake looms for Istanbul - researchers

Breakthrough seismic technology has enabled scientists to see tectonic strain building beneath the Sea of Marmara off the coast of Istanbul that could soon trigger a massive earthquake of up to 7.4 on the Richter scale, science website Phys.org reported on Tuesday. 

Researchers from Germany’s GEOMAR Helmholtz Centre for Ocean Research have demonstrated with direct seafloor measurements that considerable tectonic strain has built up on the North Anatolian fault below the sea. 

“It would be sufficient to trigger another earthquake with magnitudes between 7.1 to 7.4,” said GEOMAR geophysicist Dietrich Lange, lead author of the study published in the international journal Nature Communications.

The last time this happened, according to Lange, was in 1999 at a section of the North Anatolian fault near Izmit. That earthquake, which measured 7.6, killed more than 17,000 people and left half a million people homeless. It was the second deadliest earthquake in Turkish history.

Tectonic strain build-up along fault lines on land has been regularly monitored for years using GPS or land surveying methods. This is not possible in seabed fault zones due to the low penetration depth of the GPS satellite signals under water, according to Phys.org. 

Until now, it has only been possible to extrapolate whether plate boundaries under the Marmara are moving using land observations. The new GEOMAR system measuring acoustic distances on the seabed, while factoring in pressure and temperature fluctuations, has enabled scientists for the first time to directly measure movements with millimetre precision. 

"Our measurements show that the fault zone in the Marmara Sea is locked, and therefore, tectonic strain is building up. This is the first direct proof of the strain build-up on the seabed south of Istanbul,” said Lange, warning that release of this strain could spur an earthquake as devastating as the one in Izmit in 1999. 

https://phys.org/news/2019-07-istanbul-seafloor-earthquake.html