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German researchers warn big earthquake could hit Istanbul

The city of Istanbul is focus of great concern for earthquake scientists. The epicenter of the next big earthquake lies in the eastern Marmara Sea, in the south of the Turkish metropolitan area of Istanbul German German scientists warn. The researchers have evaluated earthquake data from two big earthquakes in the area. They have found out that while in the Western Marmara Sea, small earthquake diffuse the accumulating energy, the plates in the eastern part of the sea are locked. Energy accumulates. And the big earthquake could happen at any time.
In the report published in the “Geophysical Journal International”, the scientists warn of  of an earthquake measures 7 to 7.4 magnitude of the Richter scale.
Istanbul sits on a seismic time bomb: An arm of the North Anatolia fault line which is an active tectonic fault line, lies just 20km south of Istanbul, a city with more than 15 million people.
Im Westen des Marmarameers markieren wiederholte Beben (Sterne) ein langsames Bewegen der Platten, im Osten dagegen sind die Platten komplett verhakt (blauer Kasten)
In recent decades there have been several earthquakes, whose epicenters have been moving further westwards, the scientist stress.
Seismologists predict that the next earthquake of magnitude 7 R and higher could occur in the Marmara Sea.
The scientists predict t is most likely that the next major earthquake will occur in the eastern part of Marmara Sea “because there were hardly any subterranean movements in the past.” This suggests that the earth plates are completely interlocked in this part of the fault line  and that the tension in the ground is particularly high.
Istanbul und die Nordanatolische Verwerfung, rot: das Cinarcik-Segment im Marmara-Meer
One the other hand, there have been repeatedly weak earth tremors in the western part of the Marmara Sea, the researchers explain.
From this reason, we deduce the two plates there to a considerable extent of 25% to 75% move towards each other so that there is less accumulating energy,”  than if they were completely entangled,” Marco Bohnhoff, one of the researchers from the German Geo-ForschungsZentrum (GFZ) in Potsdam told science magazine
But where exactly will this earthquake occur? This question is crucial for the city, because it determines how much early warning time will be possible and how strong the earthquake tremors will be.

“There will be only a short early warning period of a few seconds,” Bohnhoff said adding that 
early warning times are important to switch traffic lights to red, lock tunnels and bridges, or shut down critical infrastructure.
Summary of the Research Paper published 26 April 2017

Discriminating between a creeping and a locked status of active faults is of central relevance to characterize potential rupture scenarios of future earthquakes and the associated seismic hazard for nearby population centers.

In this respect, highly similar earthquakes that repeatedly activate the same patch of an active fault portion are an important diagnostic tool to identify and possibly even quantify the amount of fault creep.

Here we present a refined hypocenter catalogue for the Marmara region in northwestern Turkey where a magnitude M up to 7.4 earthquake is expected in the near future. Based on waveform cross-correlation for selected spatial seismicity clusters we identify two magnitude M∼2.8 repeater pairs. T

These repeaters were identified as being indicative of fault creep based on the selection criteria applied to the waveforms.

They are located below the western part of the Marmara section of the North Anatolian Fault Zone (NAFZ) and are the largest reported repeaters for the larger Marmara region.

While the eastern portion of the Marmara seismic gap has been identified to be locked, only sparse information on the deformation status has been reported for its western part.

Our findings indicate that the western Marmara section deforms aseismically to a substantial extent, which reduces the probability for this region to host a nucleation point for the pending Marmara earthquake. This is important since a nucleation of the Marmara event in the west and subsequent eastward rupture propagation towards the Istanbul metropolitan region would result in a substantially higher seismic hazard and resulting risk than if the earthquake would nucleate in the east and thus propagate westward – away from the population center Istanbul. (source)

When the next mayor earthquake will occur? That is written in the …stars.

PS I remember right after the earthquake of 7.6R in August 1999 in Izmit, some 70 km east of Istanbul, seismologists were predicting a big earthquake within the next 30 years.

Big earthquakes in western Turkey often trigger earthquakes also in Greece.

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