Filenews 6 February 2022 - by Vassos Vassiliou
The earthquake of 6.1 on the Richter scale was also forgotten, although it only happened on January 11th this year, mainly because its epicentre was at sea, which contributed to not causing any casualties or damages. The Director of the Geological Survey Department, Mr. Christodoulos Hadjigeorgiou, said that if the epicentre of the earthquake was on land, things would be different.
For their part, the civil engineers reintroduced their proposal for a periodic inspection of the buildings in order to determine, each time, whether their condition is such that they can withstand the next earthquake and somewhere there the worries and discussions were exhausted until the next time. And next time again the same phenomenon will be repeated unless the next earthquake causes not only fear but also deaths and damages. Because the next strong earthquake will occur sooner or later. At least that's what the statistics say, based on which every 153 years the area of Cyprus is affected by an earthquake with a magnitude of more than 7 on the Richter scale. Every 52 years it is affected by an earthquake of more than 6.5 on the Richter scale, every 17 years it is shaken by an earthquake of more than 6 on the Richter scale, every six years by an earthquake greater than 5.5 on the Richter scale and every two years by an earthquake greater than 5 on the Richter scale.
However, these are not the only earthquakes since, as the director of the Geological Survey Department explains, the seismological centre of the Department every year records, on average, at least 2,000 earthquakes of which 1,300 have outbreaks in the wider area of Cyprus. Of these, the percentage of earthquakes felt by citizens is limited to 0.5%.
The above picture of repeated earthquakes, activated from time to time the state but what perhaps should be a requirement of society itself would be the periodic control of at least public buildings and not only the state buildings. Cinemas, churches, stadiums, large department stores, banquet halls, schools, hotels and generally places where a large number of people or employees gather.
What should also be of particular concern to those responsible is the fact that thousands of buildings were built before the implementation of the anti-seismic code which was implemented in 1994. It is noted that it was not until 1999 that the mandatory supervision of projects by civil engineers was established.
These, in combination with the fact that after 1974 (when the quarries of Pentadaktylos came into the possession of the Turks) in the free areas were used problematic materials with which thousands of buildings were built. In refugee settlements alone, 43 apartment buildings were deemed dangerous.
This is another reason why he had to keep those in charge alert. The fact that after the earthquake of 1995 thousands of buildings had been inspected by civil engineers and the finding that several of them were damaged, is also a factor that had to be taken into account. But the fact that balconies fall on buildings in Limassol or that building materials fall on buildings in Nicosia is also a worrying phenomenon.
Along with these and the fact that many buildings begin to be built without even securing planning permission and even without exercising control by the local or other authorities during the construction works. Not to mention the period when we discovered tourists and many were building uncontrollably.
In the above, the fact that Cyprus is located in an earthquake zone should be taken into account. However, the image that the seismological centre has today (and after the micro-zonal studies that are mentioned in another column) is clearly better and helps in the fortification of future buildings and by extension of their users.
Earthquakes, Cyprus and the world
According to the Geological Survey Department, Cyprus is located in the Alpine-Himalayan seismic zone, in which 15% of earthquakes occur worldwide. The seismicity of Cyprus is mainly attributed to the "Cyprus Arc", which is the tectonic boundary between the African and Eurasian lithospheric plates in the Eastern Mediterranean region. The African plate moves north to the Eurasian plate resulting in the collision of the two plates and the dive of the African plate under the microplaka of Anatolia (part of the Eurasian plate where Cyprus is located). However, when we talk about earthquakes and seismic zones, we should not consider that Cyprus was "wronged", if we consider that there is also the "Fire Zone". As the Geological Survey explains, it is a 40,000km long zone that surrounds the Pacific Ocean and that gathers 92% of the global seismicity and 75% of the global volcanic activity. This is at least what the United States Geological Survey Service (USGS) records. This is where the Pacific tectonic plate collides with the Asian plate. The Pacific plate moves to the west at a speed of 90mm per year and dives under the Asian plate. It is worth noting that the earthquake in Japan of March 11, 2011, with a magnitude of 9 degrees, which shook the world, is one of the earthquakes for which the "Fire Zone" is responsible.
The seismological system is adequate
The seismological centre of the Geological Survey Department is one of the public services which has been technologically modernized and has staff with adequacy and with little support will be able to offer much more.
As explained by the Director of Geology, the seismological stations are equipped with state-of-the-art seismometers of three components, broadband and high resolution, with digital seismographs (digitizers) and have an autonomous and unhindered power supply.
The Geological Survey Department currently operates a total of 28 seismological stations, 12 outdoor, 2 underwater and 14 ground acceleration recording stations within buildings.
All seismological stations record on a continuous basis the movement of the ground and send in real time the data, to the 2 seismological centres of Cyprus, where they are managed and processed. The new digital accelerometer network of Cyprus has been operated very recently and covers, with 14 stations recording the territorial acceleration, permanently the urban centres and temporarily specific areas in the framework of micro-zonal studies.
The performance of the Seismological Network is particularly satisfactory, with discretion that reaches the recording of earthquakes with magnitudes from 0.8 degrees Richter in some areas of Cyprus and the recording of all earthquakes of the planet with magnitudes greater than 4.8 Richter.
Micro-zonal and palaces in the sand
In order to complete the whole picture, the micro-zonal studies carried out on the initiative of the Geological Survey Department should also be taken into account, from which several interesting elements emerged, which were taken into account even in the support of the towers.
As it emerged from the micro-zone, Larnaka airport was constructed on top of two active faults, something that was taken into account during the design and construction of the project.
Microseismic studies also showed that the soils dangerous to be liquidated "descend" to a depth of up to 15 meters below the surface of the sea or land.
In the case of Larnaka, the unstable ground extends from a few hundred meters up to one and a half kilometres, while in Limassol there are areas where the unstable subsoil extends up to three kilometres from the coast.
In the case of skyscrapers, the foundation proceeds in depth until solid ground is found so as not to endanger neither the lining nor the occupants of the skyscrapers.
In general, the coastal front of the two cities is vulnerable to fluidization.
Since the 1990s, the Department has carried out micro-zonal studies initially for the wider urban area of Larnaca and then for Limassol, and Paphos, which although it is located in an earthquake-prone area, does not seem to face any particular problems. The last area for which a micro-zonal study was made was that of Famagusta. One of the issues that seems to arise concerns the stability of the soil in Paralimni Lake. Soon the micro-zone that will cover the area of Polis Chrysochous will begin.
The possibility of a tsunami is also visible
As explained in an article by the Senior Geological Officer and head of the seismological, Sylvana Pilidou, in the event of a tsunami in the sea area of Cyprus, Paphos will be the first to be hit in perhaps just 20 seconds from its occurrence. Limassol will follow in 4 minutes, Famagusta in 25 minutes and the rest of the coast of Cyprus within an hour.
The above are based on a simulation of researchers (2007) on the tsunami, although the exact time depends on the distance of an earthquake, its magnitude, the focal depth as well as other factors.
As Indicated by Mrs. Pilidou, along the southwest coast of Cyprus, which starts north of Paphos and extends at a distance of about 40 kilometres to the southern part of the Akamas peninsula, there are chaotic deposits of boulders with sand and gravel, which are a dissonance in the whole geological environment of the coastline. These boulders have a weight of several tons, angular edges and relatively fresh detachment surfaces, which leads to the conclusion that they have been deposited in the position they are in today by strong pushing forces, such as tsunamis. Similar deposits exist on almost all the coasts of Cyprus, such as Kormakitis, Karpasia, Cape Greco and Pyla, while in Ayia Napa there are areas from which the soil is absent.
Devastating earthquakes in Cyprus
Some of the major historical earthquakes are the following:
- In 16 BC a devastating earthquake in Paphos 6.5 on the Richter scale devastated the city.
- In 76 AD a devastating earthquake of 6.9 on the Richter scale affected Salamis, Paphos and Larnaca. Reports of tsunamis.
- In the years 300,332,341 AD earthquakes occurred 6.8 - 6.6 - 6.5 degrees Richter which destroyed the city of Salamis.
- In 342 AD Pafos was completely destroyed by an earthquake of 6.8 on the Richter scale.
- Earthquakes in 365-375 AD with magnitudes 6 and 7 Richter caused the complete destruction of Kourion. (It is noted that on July 21, 365, perhaps the strongest earthquake that has ever hit the Mediterranean occurred, and caused extensive damage in Greece, Crete, Asia Minor and Egypt; it is believed to have been of magnitude 8.5). A devastating mega-tsunami was caused which in Alexandria killed 50,000 people while ships were found on roofs of houses 2km from the coast.
- The 1222 earthquake of 7 degrees caused both tsunami and loss of human life. According to descriptions, "huge masses of sea water large like mountains flooded the land, demolishing buildings and filling villages with fish. Paphos suffered the most, its port was drained and the city was flooded by the sea..."
- In 1350 AD earthquake 6.5 flattened Paphos.
- In 1481 earthquake 6.3 flattened Nicosia.
- In 1735 April earthquake 6.6 in Famagusta caused 200 victims.
Vibrations from the last 115 years
- 23/2/1906: Strong earthquake 5,3 Richter. It was felt all over the island and caused significant damage to Limassol-Kolossi.
- 29 Sept. 1918: Earthquake 6,3. It was felt all over the island and especially in Larnaca and Famagusta as well as in Israel and Lebanon.
- 18 Feb. 1924: Earthquake 6 Richter that was felt mainly in the south-eastern part of the island causing minor damage in Famagusta.
- 13 Dec. 1927: 5 Richter earthquake in the Limassol area. It caused significant damage to buildings.
- May 9, 1930: 5.4 Richter earthquake. It was devastating and mainly affected the Pafos district (churches and houses in Paphos, Pegeia, Emba).
- 26 June 1937: 4.7 Richter earthquake in southwestern Cyprus. It destroyed houses and churches in Pachna, Platres, Pentalia, Omodos, Arsos, Salamis and caused landslides in Arminou.
- 20 Jan.1941: 5.9 Richter earthquake in the Eastern Mediterranean. It caused significant damage in Famagusta district (injuries and collapses of houses in Paralimni and Famagusta), damages in Nicosia and Larnaca and created a small tsunami that hit the coast of Israel.
- 9 Dec. 1947: Earthquake 5,4. It was felt throughout the island, Turkey and in Northern Israel.
- 10 Sept. 1953: Earthquake 6 Richter. A devastating double earthquake in the Paphos district. 40 people were killed, 100 injured and 4,000 were left homeless. 158 villages and towns were affected.
- 10 Sept. 1953: Earthquake 6,1 Richter.
- 15 Sept. 1961: 5.7 Richter earthquake in Larnaca
- 28 March 1984. Earthquake 4.5 Richter.
- 23 Feb. 1995: A devastating earthquake of 6.1 in the Pafos district with two dead. Several houses collapsed in the villages of Pano Arodes and Miliou.
- 9 Oct. 1996: Earthquake 6,5. Two people died of secondary causes and 20 were slightly injured.
- 11 Aug. 1999: An earthquake of 5.6 on the Richter scale, centred on the village of Gerasa.
- April 15 2015: 5.6 Richter earthquake centred on the sea area west of Kissonerga in Paphos
