Why do earthquakes occur?
Because our planet is geologically dynamic. The stiff lithospheric plates of the earth's crust, which are “floating” on the relatively more viscous interior of the earth, are in constant motion serving an important role in our planet's life: they recycle the outer shell of the Earth by giving birth to new crust or destroying aged crust by pushing it back to the interior of the planet. As a result of this movement, stress builds up at the boundaries of the plates. When the stress exceeds the critical level that can be sustained by the involved rocks, these break causing an earthquake.
Who was Engelados?
According to the Greek mythology he was the leader of the Giants and the son of Tartaros and Gaia (Earth). He played a major role during the Giants’ battle during which he was murdered by Athena, who threw at him Sicily or Mount Etna. Engelados, moving and moaning in his grave, causes volcanic eruptions and earthquakes!
Are earthquakes related to weather phenomena?
The 4th century BC Aristotle suggested that earthquakes are caused by trapped gases inside the Earth which break rocks on their way up to the earth's surface. This is most probably the reason behind the myth which relates hot and calm weather with the occurrence of earthquakes – which will bring the wind back! We know that this is not true. The earthquake occurrence is independent of the weather conditions.
Do animals sense earthquakes?
It is a fact that many animals exhibit upnormal behaviour from weeks to seconds before the occurrence of an earthquake. Many reports from antiquity until today describe such phenomena, which can be attributed to the enhanced sensitivity of animals to earthquake precursors. Such precursors can be small pre-shocks, local and small-scale variations of the electromagnetic field of the Earth and the electrical resistivity of rocks (of the fault area), changes of the level, temperature or chemical content of underground water, the release of radon, etc.
What are a seismological station and a seismological network?
Seismological stations consist of very sensitive instruments – seismometers – which continuously record the ground motion. They can detect ground displacement down to 10 millionths of a centimetre (10-7 m!) Seven seismological stations are currently in operation in Cyprus. Very soon a new network, consisting of 10 stations with up-to-date instruments, will be in full operation. The seismological data are collected in real time by the Seismological Centre in Lefkosia, where they are being processed and evaluated.
What are the measuring scale, magnitude and intensity of earthquakes?
Earthquakes occur in a variety of magnitudes, from tiny to massive. For this reason the measuring scales, in order to accommodate this vast range of magnitudes, are based on the logarithm of ground displacement measured by the seismological stations. This means that one unit of earthquake magnitude increase corresponds to 10 times more ground displacement, or 32 times more energy released. Many magnitude scales are used, the most well known being the Richter scale. The magnitude of an earthquake is indicative of the energy release at the earthquake's focus; it is unique for every earthquake and irrelevant of the point of observation. In contrast, the intensity of an earthquake is a measure of the level of its impact on humans, on structures and on the natural environment. It depends on the point of observation, the local ground characteristics, its magnitude, epicentre and depth.
Why are earthquakes not predicted?
Unfortunately the direct study of the earth's internal processes is almost impossible. Earth scientists have tested many earthquake prediction models and methods based on earthquake precursor phenomena, described above, or other theories such as that of “seismic gaps” or that of the “earthquake domino effect”. Although these approaches might, in the future, be able to predict an approximate epicentre of the upcoming earthquake, it is unlikely that they will be able to predict with useful accuracy its time of occurrence.
Which was the largest earthquake of Cyprus?
The largest earthquake of Cyprus in the last century occurred on 9 October 1996 with magnitude M=6.5 and epicentre at about 50 km off the coast of Pafos. The earthquake did not cause severe damage neither did it cause directly any loss of lives. However, the most destructive earthquake of last century was that of 10 September 1953, of magnitude M=6.1 and epicentre at the Stroumpi village of Pafos. The most destructive earthquake which hit Cyprus in the last 2000 years was most probably that of AD 76, which levelled the ancient towns of Salamina, Kition and Pafos. It is very hard to compare ancient with recent earthquakes due to the lack of quantitative data of ancient earthquakes, due to the significant differences of the built environment, and due to the subjective nature of historical records. Historical records show 26 catastrophic earthquakes in 2000 years, i.e. one destructive earthquake every 80 years. Statistical data of the last century imply, on average, one large (but not necessarily catastrophic) earthquake every 10 years. The most recent large earthquake was that of 11 August, 1999 with epicentre in the Gerasa village of Lemesos. There is no way, however, of knowing whether the Earth will continue exhibiting geological phenomena at the same rate, so statistical data should not be taken as a rule.
What should I do or NOT do during an earthquake?
Stay calm – panic causes victims.
If you are INSIDE A BUILDING, stay there! Protect yourself under a solid table, or stand beside an internal wall. Stay away from windows, fire places and hanging objects. Get out of the kitchen. Do not run down the stairs or outside. Do not use an elevator.
If you are OUTSIDE, go to an open area away from buildings, electrical cables and poles, chimneys and anything else that can fall on you.
If you are DRIVING, stop carefully away from bridges, trees, electrical cables and poles. Stay inside the car until tremor stops.
If you are at the MOUNTAINS, be cautious of falling rocks, trees, etc.
If you are near the BEACH, move away from the coast to high altitude ground.