“The big and small earthquakes in recent days are caused by lithospheric fractures throughout Greece. Most of them are superficial, that is, they have a depth of up to 50 kilometers. But in the southern Aegean there are earthquakes and intermediate depths with huts reaching 200 kilometers. This is due to the fact that the African lithospheric plate curves along the Greek arc and sinks inside the Earth. Due to the same process, at a depth of about 150 kilometers, a hot magma is produced that rises to the surface and forms the volcanic arc of the southern Aegean with major volcanic centers in Santorini and Nisyros, which are considered active volcanoes. In Methana the volcano is rather active, while in Milos and Kos, volcanoes are now inactive. In all volcanic centers, however,
“The history of earthquakes in Greece goes back a long way. There are written sources beginning with Herodotus, the father of history, reaching classical antiquity (eg Thucydides) and then, in Hellenistic and Byzantine times, in Arab and Venetian rule, in the Ottoman era and ending in modern times. earthquakes began around 1900. Even before, we have witnessed strong earthquakes, from the traces they left behind on the ground and in archaeological sites, ”notes Papadopoulos, adding:
“The issue with our country is not just that there are many earthquakes, nor that it has the highest seismicity in all of Western Eurasia, that is, from the Urals we were the Atlantic and from Africa to the North Pole. It is also that the seismicity in Greece is of great complexity and is related not only to one type of fault, but to all the major types of fault that we encounter on the planet. The lithosphere in the geographical area of our country and the surrounding areas is literally fragmented because this region is crushed between the African plate moving to the NE and the Eurasian moving towards the southwest, with a relative movement reaching them. 6cm a year along the Greek bow ”.
The Greek arc extends from the Ionian Islands to the south of the Peloponnese and through Crete and Karpathos ends in Rhodes and southwestern Turkey. At the same time, the small lithosphere of Anatolia, practically the geographical region of Turkey, is also moving west and southwest, complementing the field of lithosphere forces in Greece. In short, if the activity of the lithospheric plates continues at the same or even faster pace, the maps of the future will depict Greece as a hug with Turkey. However, shaping the land on the planet is an old and permanent affair. The point is what happens during it …
“The result of this mobility in the Earth’s lithosphere is the very high seismicity that is statistically expressed in Greece with a magnitude 6 earthquake on the Richter scale, or greater, about every year,” notes Papadopoulos and explains: “The frequency of occurrence, however, the magnitude of the earthquakes is smaller. And vice versa. Large earthquakes are more rare. For example, 7-magnitude earthquakes recur approximately every 10-12 years and even larger ones are more sparse. The last 7th, for the precision 6.9 Richter we had in our country, was on May 24, 2014 in the northern Aegean. You, the people do not remember him, because he did not cause disasters. But it was a strong earthquake, as expected. “
On earthquake activity worldwide, Mr. Papadopoulos notes that there are between 15 and 18 earthquakes measuring 7 on the Richter scale each year. And if anything more is observed at this frequency, then it is no accident.
The history of earthquakes in Greece
The largest earthquake recorded in Greece was about 8.5 magnitude on the Richter Scale and occurred on July 21, 365 AD. in western Crete, where the coastal zone was raised by 6.5 meters. At the same time, a savage tsunami flooded the entire eastern Mediterranean basin. The recurrence of the phenomenon was recorded on August 8, 1303, with the exception that this time the earthquake occurred on the eastern side of Crete.
The next major earthquake was recorded on October 12, 1856, focusing on the sea area between Crete and Rhodes and measuring 8.2 on the Richter scale. The earthquake destroys seven villages in Crete and leaves behind Crete, Rhodes, Karpathos, Kassos, Symi, Kastelorizo, Amorgos and Cyprus with 618 dead, 638 injured and around 17,000 homes destroyed or seriously damaged.
But it is also rich in seismic activity throughout the 20th century, during which, according to the Athens Observatory, 37 deadly earthquakes ranged in magnitude 6 to 8 on the Richter scale and countless smaller. The strongest hits of Enceladus are recorded on 11 August 1903 and 26 June 1926 with 7.2 Richter and 8 Richter in Kythira and Rhodes respectively. Compared to the aftermath of the aftershocks, they do not look dramatic, as 14 were dead in Kythera and 12 in Rhodes. However, if you consider the number of houses and inhabitants of the islands of that time, the numbers are certainly not negligible.
“The magnitude of an earthquake does not depend solely on its size. There must be many factors at the same time. The size, the structure of the soil, the quality of the houses, the time and duration of the vibration, etc. ”, explains Mr. Papadopoulos.
However, the most deadly earthquake of the previous century struck on August 12, 1953, the island complex of Kefalonia-Zakynthos-Ithaca, which recorded a total of 455 dead, 21 missing and 2,412 injured. An indication of the severity of the earthquake was the fact that of the 33,300 houses on the three islands, more than 5,000 were erected. Indicative are the headlines of the newspapers of the time … “Kefallinia, Zakynthos, Ithaca are absent from yesterday” published in a headline on August 13, 1953 in the newspaper “ELEFTHERIA”.
Predicting earthquakes is a feasible task
Mr Papadopoulos explains that, in fact, a short-term forecast sounds impossible. “Seismology is exactly the opposite of meteorology. The second, recording visible phenomena may take some days, but not longer. But when you are dealing with what is going on inside the earth, you do not see it, you record and study the movements and calculate the depth of time. Therefore, the short-term forecast sounds utopian and the question is self-evident … “But now, Dr. Papadopoulos, do you really think we will ever be able to predict earthquakes?”. But the answer is vertical. “Beyond any doubt”
-How, that is?
“With research and observation. When you seriously and systematically monitor an area with rich seismic activity, you can predict the large earthquake by recording its seismic sequence. In this study, scientific research converges worldwide ”.
-And how does a scientist know that one of the earthquakes is not the master?
“The earthquakes have the following three characteristics: they are spatially close to each other, their time progresses increasing, that is, they increase with the high vibration and finally, as we approach the main earthquake, the magnitude of the earthquake increases. By the time the size and magnitude of the vibrations that follow, the aftershocks are decreasing. “
“It is impossible to avoid earthquakes. But we can learn to deal with them, “Mr. Papadopoulos emphasizes, and says:” Putting education and regulations in place in our lives. ”
Source of information / PHOTO: RES – EIA