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Why did Zakynthos move 3cm on 25 October 2018?

A year ago today, Zakynthos was hit by a large 6.8R earthquake. It struck the island on 25 October 2018 at 22.54pm (UTC) The earthquake was 56.9km SW of the island, around 11km deep. The earthquake was followed by aftershocks, a number of which were around 5R, and the aftershocks continued for many days and months, eventually dissipating over the late spring, early summer months of 2019.
A few days after the earthquake it was reported that during the event the island moved a small distance. Experts say that after analysing satellite and seismic data, Zakynthos shifted south west by approx. 3cm. At the time the news both puzzled and worried some people – despite 3cm being a minute distance – and many asked if it was normal? The answer was yes, a movement during a large event like this was perfectly normal.

Science

The earth is made up of constantly shifting landmasses. These landmasses are on a floating set of tectonic plates that move and bump into each other. During this action of movement and bumping, earthquakes occur and in some instances volcanoes erupt due to the pressure that needs to be released. It’s a perfectly natural phenomenon and one that has been happening for billions of years. The worlds landmasses used to look a very different; a “single” landmass called, Pangaea. But over time this landmass changed and separated and ended up as the “world map” we are all familiar with today all down to the continual jolting of the earth and movement and creation of landmasses by these very earthquakes and volcanoes.

Today the earth is still moving, still shifting and still creating. Volcanic eruptions of Kīlauea in Hawaii over the last few years have seen new pieces of land formed from lava that has spewed from the main volcano; it’s an island that is continually growing and evolving. Two of the most well known tectonic plates, the North American and the Eurasian (separated by the mid-atlantic ridge) are constantly moving away from each other, and experts have estimated that they are getting further apart by around 2.3cm a year. In Africa, the East African rift is continuing to develop, caused by the Somali and Nubian plates moving away from each other by around 6-7mm a year. 

The Divergent rift, Iceland
The East African Rift

The Great Ionian Earthquake, 1953

In 1953, when the Great Ionian earthquake struck, its epicentre was in Kefalonia. Dependant on which scientific institution you choose to refer to, the earthquake was measured at either 7.0R or 6.8R, and occurred at 9.23am. It was followed by some smaller aftershocks and then another earthquake 6.3R that took place at 12.05pm. These earthquakes were large enough to not only destroy buildings but an entire town, they created large cracks and were felt in many other countries. Fires broke out and many people were also sadly injured and killed. After things had settled down, it was confirmed by experts that this great 1953 earthquake had raised the island of Kefalonia by 60cms (24 inches)!

The 6.8R earthquake of October 2018, on Zakynthos was worrying for many people, it was a huge jolt that was followed by a large amount of aftershocks, it unsettled the island and was even reported worldwide. The difference between the 2018 earthquake and 1953 however, is the fact that so many of the islands buildings survived this time, having been built to strict earthquake codes – although over 100 homes and businesses across in Zakynthos, in its main Town, Laganas, Lagapodo and Macherado were confirmed as having some damage that required repairs. Yes, a few older buildings such as Strofades Monastery etc. did also suffer some damage, and sadly this does occur with the islands older buildings, but the positive news was that no one was seriously injured and neither was anyone killed.

Tectonic Future of Zakynthos

Zakynthos, like so many places around the world, is in an earthquake zone, in fact there have been other periods between 1953 and 2018 where “higher” than normal earthquakes (6R+) have struck with a number of aftershocks that followed, unsettling residents for a few days. These dates include 1965, 1966, 1972, 1983, 1988, 1997, 2003 and 2006. Like the earthquake a year ago, there was a lot less damage than in 1953 and injuries were sparse or none at all. Zakynthos authorities are incredibly well prepared for such events, and as many can see from the difference between 1953 and 2018, the island is now much better equipped to cope in the future. Sometimes as the evidence shows these events do cause land movement, either by pushing up or through an upwards thrust. Some parts of the earth are just continuing to move and evolve at a steady rate of their own accord. So, with that in mind Zakynthos moving by 3cm doesn’t seem to be such a strange occurrence after all, it’s just a natural part of the earths continued evolution, and one that will continue many years into the future, not just in Zakynthos, but across the entire world.

About Chrissie Parker

Chrissie Parker joined the Zakynthos Informer Team in 2014. Chrissie’s first experience of the island was a combined birthday and wedding celebration, in true Zakynthian style. Since then she has been able to combine her love of the island, including its incredible history, tradition and culture, with her love of writing.

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