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10/31/07

Risk of Tsunamis in Caspian Sea should be taken seriously


According to researches by the experts in International Institute of Earthquake Engineering and Seismology, and based on geological and historical data, the Caspian Sea, although not connected to the open sea, can be the origin of tsunamis.

Engineer Sahar Amirinezhad, a post graduate of Mines Department of Tehran University, who has written a Thesis, supervised by Dr Mehdi Zare'i, head of the International Institute of Earthquake Engineering and Seismology, said in an interview with Thesis reporter of ISNA: Working on the risks of tsunami in Caspian Sea borders, we used a model simulating the conditions of the Caspian Sea and its potentials of originating a tsunami. Following this model we can then proceed in zoning the tsunamis risk on the borders of the sea. In the preliminary studies it was revealed that the Caspian Sea, the biggest lake in the world, has a geological structure very similar to open seas and has height displacements at the bottom of the sea. Therefore it can be assessed that there is always a risk of tsunamis in the Caspian Sea, just like the Marmara Sea which is even smaller than the Caspian.

She added: There is a considerable difference of depth between the northern, central and southern parts of the Caspian Sea; this is an important factor in determining the height of waves and the possibility of tsunamis. The depth in the northern parts is very shallow (12 to 15 meters) and is sometimes frozen, while the depth of water reaches 700 meters in its central parts and 1100 meters in the southern parts. Although this depth is not comparable to the depth of water in oceans but it is not a shallow depth by any standards.

Amirinezhad pointed out to the geological configuration of the sea bed in the Caspian Sea and its earthquake potentials and added: From a seismotectonic point of view, the Caspian Sea is located in the southern Caspian tectonic belt area and coincides with the undersea mountain of Sert and is connected from the other side to the Upsheron region in Armenia and thus creates a huge difference in depths of this sea.

She asserted: In this model the seismotectonic impact of activation of this earthquake fault in the Caucasian mountains on Caspian Sea was studied, which demonstrated that in case of such an earthquake there is possibility of producing waves with 3.5 meters of height which can penetrate over 100 meters into the mainland. 

Although tsunamis with less tall waves would cause less damage compared to ocean tsunamis , but considering the population density in cities bordering the Caspian Sea and regarding the built up areas and strategic oil related structures very close to the sea, the risk of tsunamis in this area should be taken seriously.

Amirinezhad insisted that historical evidence supports the seriousness of tsunamis; these are the report of a tsunamis on 8 July 1895 in Turkman port in Turkmenistan following an earthquake of an amplitude of 8 on the Richter scale and causing large damages and also 10 to 15 reports about suspected tsunamis. She added earthquakes with an amplitude of 6.5 to 7 Richter in the seas as well as under water volcanoes and aerolites having a diameter larger than 20 meters are at the origin of tsunamis.

She asserted: Considering the difference if depth and the phenomenon of land sliding on the sea bed, are other factors responsible for creating tsunamis. This is more probable in the middle of the Caspian Sea.

Amirinezhad said to ISNA: According to statistics, 58 percent of tsunamis have occurred in the Pacific Ocean, 25 percent in Mediterranean Sea, 12 in Atlas Ocean,  and 5 percent in Indian Ocean. According to more accurate estimations 76 percent of tsunamis have occurred in the Pacific Ocean, 10 percent in Mediterranean Sea, 9 in Atlas Ocean, and 5 percent in the Indian Ocean. The most damaging tsunami was the one on 2004 in the Indian Ocean.

She pointed out that the time interval between an earthquake and the waves of tsunami is between 5 to 6 hours and said: According to the tsunami zoning maps, the borders of the sea should be free from building and population and there should be online alarm systems connected to the world's seismotectonic centres which can in fact reduce the risk and damage. Building barriers and dams, with a height about the double of the wave height could also reduce the damages which could be brought about by tsunami.

Note: Original article published in Persian by ISNA.
Translated for Payvand.com by BMarz translators: http://www.BMarz.com

 

... Payvand News - 10/31/07 ... --



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