Is TRNC earthquake ready?
LAST Saturday an earthquake shook Cyprus. GÜLDEREN ÖZTANSU looks at the history of Cyprus earthquakes, the risk of tsunamis and how prepared the TRNC is for a disaster.
AN UNDERSEA earthquake occurred in the Gulf of Antalya on Saturday, December 5, which was felt in Turkey and Cyprus and reportedly as far as Rhodes, Egypt, Israel, Jordan, Lebanon and Syria.
The earthquake’s epicentre was 63km south-west of the Turkish town of Alanya. Two people were hospitalised in Turkey due to the panic caused, including a man who jumped from the second floor of a building.
Turkey’s Disaster and Emergency Management Authority (Afad) said the quake measured 5.2 on the Richter scale, while the TRNC Meteorology Office, which also collects seismological data, reported the magnitude to be 5.5. The South’s Geological Survey Department of Cyprus declared its strength as 5.4.
It took place 77.58km below the surface, Afad reported. According to the TRNC Met Office, this makes it a
“medium-depth earthquake” as it falls between 70km and 300km in depth.
“Medium-depth earthquakes tend to extend over a larger surface area and they are not as destructive as shallow earthquakes,” the Met Office said, adding that such earthquakes “often occur where one tectonic plate subducts under another”.
This type of tectonic boundary is called a “convergent plate boundary” and they cause the deepest and the most powerful earthquakes.
Prof Dr Cavit Atalar, head of Near East University’s Earthquake and Soil Research and Evaluation Centre, told CyprusToday that the island is a “total earthquake country” with “15 or 16 destructive earthquakes” recorded since 1994, when seismographs were first used in Cyprus to accurately measure seismic activity.
The seismicity of Cyprus is mainly attributed to the “Cyprus Arc”, the tectonic boundary between the African and Eurasian lithosphere. As the African plate moves north, it is pushed under the Anatolian “microplate” which is an outlier of the much larger Eurasian plate.
The “Cyprus Arc” lies within the second largest earthquake-stricken zone on Earth, stretching from the Atlantic Ocean, across the Mediterranean basin, through Greece, Turkey, Iran and India and as far as the Pacific Ocean.
The geological uplift of Cyprus and the “Cyprus Arc” are both products of the tectonic activity in the Mediterranean.
However, Cyprus is now caught between these plates, which formed the island itself, meaning that it must be prepared for a disaster.
According to the Geological Survey Department of Cyprus “the time distribution of seismic activity is not ‘normal’.”
The department, which has studied historical and recent earthquakes, points to findings that illustrate how there are periods of intense activity followed by periods of “seismic recession”.
“For example, in the years 1995 to 1999 there was an increase in seismic activity with strong earthquakes of magnitude 5.6 to 6.8 on the Richter scale, while in the previous four decades there was a relative recession,” it said.
Costas Papazachos, a professor of Geophysics at the Aristotle University of Thessaloniki, and his colleagues con
ducted of Eastern recurrence a Mediterranean. statistical of local earthquakes in the study on the periods
Their findings suggest that an earthquake measuring above 7.0 on the Richter scale occurs roughly once every 153 years in the Eastern Mediterranean region, while earthquakes of a magnitude over 6.5 occur twice in a 52-year period. Quakes measuring over 6.0 happen six times over 17 years; 17
earthquakes larger than 5.5 happen over a six-year period; and 50 tremors that exceed 5.0 occur every two years.
It is estimated that since 1900 Cyprus has been hit by 800 earthquakes of magnitudes ranging from 4.0 to 7.0 on the Richter scale – 21 of which were above magnitude 5.0.
The strongest earthquake of the last 120 years was recorded in 1996 off the coast of Paphos, with a magnitude of 6.8
on the Richter scale.
Exactly how prepared is North Cyprus for a destructive earthquake? Prof Atalar argues that it is not earthquakes – which happen all the time across the globe – that threaten our safety, but poorly constructed buildings as they are a significant factor for determining the level of destruction.
Asked about seismic activity in recent years, Prof Atalar said: “It does not matter if the seismic activity has been high or low. We look at statistics to identify trends yet seismic activity is a domain where it is not guaranteed what can happen and when.”
The earthquake last Saturday scared people, he said, because “North Cyprus is not prepared for a large earthquake”.
“Sturdy buildings are found on sturdy surfaces,” Prof Atalar explained. “Cyprus has one of the most problematic surfaces in the region as 45 per cent of the ground is clay, which swells.
“The 2002 ‘ Swollen Clay Project’, under my leadership, attracted attention to the fact that clay swells and then causes harm to the buildings on top of it, creating financial cost and greater vulnerability towards tectonic hazards.”
Adding that “almost every building was sturdy in the October earthquake of İzmir” in Turkey, Prof Atalar highlighted the significance of the relationship between geomorphology – the study of the physical features of the surface of the earth and their relation to its geological structures – and land use.
“The earthquake [in İzmir] was destructive as the soil type was ignored during construction. Similarly for the August 17, 1999 [İzmit] earthquake [in Turkey], where 20,000 people died, 66 per cent of the buildings were built on the wrong surface.”
In North Cyprus “the features of the soil are not accounted for during construction”.
“A single construction plan is used across the island thousands of times regardless of the type of soil the plan is mapped onto,” Prof Atalar continued.
“Buildings are not built in accordance with the geochemistry of the surface. We have to build based on the features of the surface to protect people.
“I want our people and our government to know that the part geomorphology plays is huge.
“Everyone must think a lot before starting a construction. Buildings, including Lefkoşa State Hospital, must be made at higher, safer locations and on the proper type of soil, where they will not be subjected to floods, as the state hospital was in 2010.
“Underground water levels have an impact on the lifting capacity of surfaces. A building located near a stream will hold different qualities in summer and winter based on the impact of rainfall on underground water reserves.
“The capacity [of the ground to hold weight] changes from 16 tonnes to 30 tonnes per square metre. This can cause liquefaction and even has an impact on the journey of seismic waves that cause an earthquake.”
Prof Atalar said that “such mistakes are common in Cyprus”, giving the example of new buildings on a “swamp” near the Soli harbour.
He added that North Cyprus adopted Turkey’s earthquake building regulations in 1975 but that houses built according to those laws are “no longer deemed acceptable under the new 2019 regulations”.
Even earthquakes of “smaller magnitudes” can cause “a very high rate of destruction” as a result, Prof Atalar warned.