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Paleoseismology of the Anatolian and Caucasus Region

"The people of Behura fled from my weapons into the mountains of Uschkiani and Banni. I surrounded part of them and killed all. The others that could flee were burned by the earth god Teischeba."
Description of the military campaign of king Argischti I in 780-756 B.C.

Turkey is characterized by two main strike-slip fault systems - the North Anatolian Fault (NAF) and the East Anatolian Fault - that in the Caucasus region merge together in a complex tectonic system dominated by compressional thrust faulting. 
Devastating earthquakes of the last decades occurred mainly along the dextral North Anatolian Fault that forms the plate boundary between the Anatolian and Eurasian plates. This is also a densely populated region with the city of Istanbul as one of the most important harbours of the Mediterranean Sea. 
May 10, 1566 the cities of Rossana and Constantinople (modern Istanbul) were hit by an earthquake that caused the collapse of buildings. Some 50 years earlier (October 10, 1509) Constantinople had been affected by an even worse disaster, killing 13.000 people. 
During the 20th century seismic activity apparently moved along the NAF from the east to the west, in 1999 two strong earthquakes hit the city of Izmit, killing 17.000 people.

In Armenia the strongest earthquake since centuries occurred December 7, 1988, it destroyed the city of Spitak and killed 25.000 people.

Fig.1. Simplified tectonic map of the Caucasus region with the locations of important earthquakes - the recent earthquake at Van, the earthquake of Spitak and the historic earthquake of Behura. Various sections of the North Anatolian Fault show a progressive younger activity from the east to the west (colour coded). According to some models this could suggest that stress is released following the fault system and that Istanbul could be hit again by a stronger earthquake in the future.

The region around Lake Van was repeatedly hit in the present and the past by strong earthquakes. Cronicles report of havoc and destruction in the 4th century and again in the 10th century, in 1976 an earthquake in the Van Province caused 4.000 victims.

One of the oldest earthquakes in the Caucasus region was inferred from historic descriptions and confirmed by geologic evidence -it dates back to more than 2.700 years. 
A French-Armenian team of paleoseismologists searching for suitable sites for their research discovered on aerial photographies the ruins of the ancient city of Behura.
Paleoseismology tries to collect evidence for earthquakes based on both archaeological as geologic proxies to improve the knowledge of the seismic history of a region. Knowing this history of a region can help to estimate the time-intervals occurring between earthquakes of a certain magnitude.
Ancient documents refer to a city located in the area around the Lake Sevan that was conquered in 780 to 756 B.C. by the great king Argischti I, the description of the siege is curious, mentioning fire, ash and clouds (send supposedly by the earth god Teischeba) helping destroying the city. Maybe this is the description of a volcanic eruption accompanied by earthquakes. Nearby the site relatively unweathered and therefore probably young lava flows coming from the volcano Porak were discovered,
In Behura the excavation of a trench revealed a complex stratigraphy of soils, a displaced wall, scree deposits and younger soils, suggesting that the city was in fact destroyed by an earthquake.

Bibliography:

HERVÈ, P. & KARAKHANIAN, A. (2001): Der Untergand von Behura. Spektrum der Wissenschaft -Dossier 2 "Die Unruhige Erde": 31-35
JACOB, K. (2006): Istanbul - Warten auf den großen Schlag. Bild der Wissenschaft 2: 48-53

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