Earthquakes, (somestimes also known as tremors) are an effect that occurs when the earth's crust releases energy, that is transformed into seismic waves. Earthquakes are measured by a scale called "Magnitude" wich measures the earthquakes strenght in a scale using numbers.
Earthquakes that measure a magnitude of 2 or 3 for example, are the ones we rarely feel, and occur most frequently, however an Earthquake of magnitude 7 or 6, causes serious damage to a location and usually cover a large area, the size of an entire city sometimes. As most of you know, we can feel earthquakes when the ground starts shaking, the ammount of shaking however, is measured by the Marcalli scale.
The epicenter of an earthquake, is the place where the earthquake origins, and the closer one is to the epicenter, the larger is the strenght of the tremor. Earthquakes are often strong enough to set off volcanos, and cause landslides, with adds to their danger and destruction power. Naturally, earthquakes are caused by the colliding of the tectonic plates (the world has 8 major tectonic plates, and many smaller ones) wich when they do collide, starts shaking due to the force of the impact. An Aftershock or Foreshock, is an earthquake that occurs after or before a stronger earthquake, respectively , with the aftershock or foreshock having smaller magnitude than the original earthquake. When the epicenter of an earthquake is located in the ocean, it might release a tsunami.
However, there are already some skyscrappers and building with advanced counter-measures to avoid earthquakes, and they usually work very well. Below is a small video by the National Geographic channel on youtube, wich depicts what happens during a tremor.
Pedro Batim
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