Friday 27 September 2019

Magnitude 5.8 Earthquake beneath the Sea of Marmara.

The Turkish Disaster and Emergency Management Authority has reported a Magnitude 5.8 Earthquake at a depth of 6.9 km beneath the Sea of Marmara, which occurred slightly before 2.00 pm local time (slightly before 11.00 am GMT) on Thursday 26 September 2019. The event was felt across northwest Turkey as well as in parts of Greece and Bulgaria, and has been linked to 43 injuries in the city of Istanbul, mostly caused by people trying to evacuate crowded buildings rapidly in a city where planning regulations are notoriously week.

The approximate location of the 26 September 2019 Sea of Marmara Earthquake. USGS.

The Sea of Marmara lies on the North Anatolian Fault Zone, which separates the Eurasian Plate to the North from the Anatolian Plate to the South. The majority of Asian Turkey lies on the Anatolian Plate, which is being pushed to the west by the northward movement of the Arabian Plate, which is in turn being pushed by the African Plate, further to the south. This creates as zone of faulting along the northern part of Turkey, the North Anatolian Fault Zone, as the Anatolian Plate is pushed past the Eurasian Plate, which underlies the Black Sea and Balkan Peninsula  (transform faulting). This is not a simple process, as the two plates constantly stick together, then break apart as the pressure builds up, leading to Earthquakes, which can be some distance from the actual fault zone.

 Plate movements and fault zones around the Anatolian Plate. Mike Norton/Wikimedia Commons.

The northward movement of the African and Arabian Plates also causes folding and uplift in the Caucasus Mountains, which separate Georgia from Russia. Again this is not a smooth process, with the rocks sticking together, then moving sharply as the pressure builds up enough to break them apart, which can also lead to Earthquakes in the region.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organisation Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.

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