12 May 2015
| Last updated on 19 May 2015
What Causes Earthquakes?
If you're moving to a country that is prone to experiencing earthquakes, you may be interested in knowing why they happen and what causes them.
Whether it's a small or large one, experiencing an earthquake is terrifying. Due to the Earth's structure, it's inevitable that most expats living in foreign countries will at one point live through an earthquake in their adopted country.
The surface of the Earth, as scary as it sounds, is in continuous slow motion, and the plate tectonics, which cover Earth's entire surface) move, rub against each other and sometimes sink beneath each other. Because of this movement, we tiny humans on the very surface can sometimes feel the vibrations caused by these gigantic rocks moving, rubbing together and eventually breaking under stress. Sometimes, an earthquake can be caused by what is known as a 'strain' movement, whereby two plates are stuck together, but the rest of the plate(s) continue to move, causing a lurch when the eventually partition.
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Plate tectonics are pieces of the Earth's crust, and are around 100 km thick and consist of two principal types of material; oceanic crust, continental crust. Today, there are aroudn seven major plates that comprise the bulk of the continents and Pacific Ocean; African, Antarctic, Eurasian, Indo-Australian, North America, Pacific and South American along with several other smaller, secondary plates.
SEE ALSO: What to do during an earthquake
The size or magnitude of an earthquake is determined by measuring the amplitude of the seismic waves recorded on a seismograph, and the distance of the seismograph from the earthquake. These are effectively put into a formula, which converts them to a magnitude, which is a measure of the energy released by the earthquake.
Of course, with such movement happening below as at all times, fortunately any smaller earthquakes that occur (which are more frequently, in fact) cause little or no damage, and may even go unnoticed.
The point inside the Earth's crust where the pressure between moving rocks is released is called the focus, which is where it originated within the Earth. The earthquake's epicentre is the point on the Earth's surface directly abouve the focus. An earthquake's energy is released in seismic waves. These waves spread out from the focus. The waves are felt most strongly at the epicentre, becoming less strong as they travel further away. The most severe damage caused by an earthquake, therefore, will happen close to the epicentre.
What's most devastating about earthquakes is their effect on human kind. Entire settlements can be destroyed, and large numbers of lives can be lost. Plus with added aftershocks, more and more damage can occur. Homes may be destroyed, transport and communication links may be disrupted. Even water pipes may burst, leaving water supplies contaminated.
