A earthquake , earthquake or seism is a ground shake produced by forces acting inside the planet . The word earthquake comes from Latin terraemotus, while earthquake derives from a Greek word that means, precisely, "shake" .
The shaking of the ground occurs with the shock of tectonic plates , which are fragments of the lithosphere (the most superficial layer of the land ) that move like a rigid block, without an internal deformation on the asthenosphere (the immediate layer to the lithosphere, which is between about 100 and about 240 kilometers below the surface).
Another cause of earthquakes is the reorganization of the components of the earth's crust that releases a lot of Energy , either by volcanic processes, hillside movements or the potential elastic energy that accumulates with the gradual deformation of the rocks that are next to an active fault.
The inner point of the planet where the earthquake takes place is known as seismic focus or hypocenter . On the other hand, the point of the surface that is in the vertical of the hypocenter (that is, it is located perpendicular to it) is called the epicenter.
Seismic movements propagate through elastic waves from the hypocenter. There are three major types of seismic waves : the primary waves , longitudinal or P (they propagate in the same direction as the vibration of the particles); the secondary waves , transversal or S (they propagate perpendicular to the sense of vibration of the particles); and the surface waves (They occur on the earth's surface as a result of the interaction between primary and secondary waves).
The most violent earthquakes in history
This catastrophe it does not contemplate social classes nor does it notify well in advance when it will take place; such is that its consequences can be many times atrocious, devastating regions and entire countries, with the consequent deaths of its inhabitants.
Throughout the history of mankind there have been countless earthquakes, among the strongest are the following:
* Japan earthquake of March 2011: It is undoubtedly the strongest in history and reached 8.9 degrees on the Richter scale.
* Valparaíso earthquake (Chile) of July 1730: one of the most serious suffered in this country that, like the last one that took place in Japan, was followed by a tsunami which swept several kilometers off the coast. The quake reached 8.7 degrees on the Richter scale and the tsunami waves, 14 meters high.
* Lisbon earthquake (Portugal) November 1755: it was an earthquake that almost exceeds 8.7 degrees on the Richter scale; These were moments of great tension, especially since it was not only accompanied by a tsunami but also with important fires. In total more than 10,000 people died.
* Rat Island Earthquake (Alaska) February 1965: also this earthquake was followed by a tsunami, with waves up to 10 meters high, and that caused damage to the coast. The vestiges of this earthquake were perceived in all the countries of Central America, in Japan and Russia.
* Ecuador Earthquake of January 1906: its relevance is due to the fact that it was a tragedy that affected several affected countries, including Panama, Mexico, Japan, California and Colombia.
* Chile earthquake of February 2010: It was the strongest earthquake in this country, reached 8.8 degrees on the Richter scale and claimed the lives of 521 people.