Earthquakes can also happen in Poland
– Seismic risk always exists, in Poland it is very low, although it is not zero – believes prof. Zbigniew Zembaty, Dean of the Faculty of Civil Engineering and Architecture of the Opole University of Technology. As he recalls, the effects of the earthquake in Krakow were written by, among others, Jan Dlugosz.
As pointed out by prof. dr hab. Eng. Zbigniew Zembaty, there are practically no places on the globe that are completely free from the risk of an earthquake. The scientist reminds that the chronicler Jan Długosz wrote in the 15th century about the collapse of the church vault in Krakow as a result of an earthquake, the epicenter of which was in today’s Slovakia.
“In 2004, two weak earthquakes were recorded in Poland, which caused minor damage to buildings. The entire southern border of Poland should formally be the weakest zone of the construction seismic standard. in the Czech Republic and Slovakia there is a design standard with a weak seismic zone” – added the scientist. He noted that in the last 10,000 years, especially in the Carpathian region, earthquakes with their epicenters in Poland could have taken place.
Professor Zembaty’s team, in cooperation with the Hungarian Academy of Sciences, is conducting paleoseismological research aimed at finding an answer to the question of how large the tectonic movements could have been in a given area. One way is to study the structures of stalagmites growing over thousands of years. The results of these studies are particularly useful in determining the seismic risk for particularly strategic structures – e.g. nuclear power plants.
“While normal seismic standards take 475 years for expected phenomena to return, 10,000 years are used for nuclear power plant design standards. If we take into account such a long period, it turns out that there are no places on the globe free of possible seismic phenomena. It is worth emphasizing that even in a very seismically calm area, such as Finland, a return period of up to 100,000 years was used in the design of the local nuclear power plant. How big can earthquakes with a return period of 10,000 years be? years in highly seismically active areas is evidenced by the quite seriously considered hypothesis that the biblical flood could be an echo of a real phenomenon consisting in the opening of the Bosphorus Strait as a result of a huge earthquake and the flooding of a huge, inhabited depression located at the bottom of today’s Black Sea” – the scientist emphasised.
Referring to the recent earthquake in Turkey and the enormous scale of damage, the scientist drew attention to both the construction standards adopted in this country in areas at risk of seismic activity, as well as the practical approach to their compliance by designers and contractors. He considers the technical and construction standards used in Japan to be exemplary in this respect.
“When it comes to countries that are at high risk of catastrophic earthquakes, such as Japan, you also have to think about whether simple amplification will be enough. It is important to remember that each reinforcement adds mass to the building. In turn, each addition of mass increases the seismic forces. That is why low, wooden buildings are better than large, reinforced concrete structures. During my stay in Japan, I was at the construction site of a building that was erected on vibration isolators. Such eight powerful drum structures composed of alternating steel, rubber, steel, rubber – covered by a patent – supported a large, ten-storey building. The general idea is that when the ground moves, the structure should respond with some delay. This is insurance against these really catastrophic earthquakes” – noted Professor Zembaty.
The scientist recalled that during the 2011 earthquake, which caused a giant tsunami, no one died as a result of damage to buildings.
“While in Tokyo, I was staying on the 15th floor of a hotel when this happened – but the shock was relatively weak for Japan. At magnitude five, we ended up with building vibrations and strange acoustic effects related to the overloading of the structure” – the scientist said. (PAP)
Author: Marek Szczepanik