An earthquake is a shaking of the ground caused by internal forces of the planet.
An earthquake is a shaking of the ground caused by forces acting within the planet . The phenomenon can also be referred to as a seismo or seismic. The word earthquake comes from the Latin terraemotus , while seismo comes from a Greek word meaning, precisely, "shake."
Earthquakes occur when tectonic plates collide , fragments of the lithosphere (the most superficial layer of the Earth ) that move as a rigid block, without causing internal deformation in the asthenosphere (the layer immediately following the lithosphere, which is located between 100 and 240 kilometres below the surface).
Another cause of earthquakes is the reorganization of the components of the Earth's crust that releases a large amount of energy , either by volcanic processes, slope movements or the elastic potential energy that accumulates with the gradual deformation of the rocks that are next to an active fault.
Characteristics of an earthquake
The interior point of the planet where the earthquake takes place is known as the seismic focus or hypocenter . On the other hand, the point on the surface that is located vertically from the hypocenter (that is, perpendicular to it) is called the epicenter .
Seismic movements propagate through elastic waves from the hypocenter. There are three major types of seismic waves : primary , longitudinal or P waves (they propagate in the same direction as the vibration of the particles); secondary , transverse or S waves (they propagate perpendicular to the direction of vibration of the particles); and surface waves (they occur on the Earth's surface as a result of the interaction between primary and secondary waves).
Typically, earthquake tremors are caused by a collision of tectonic plates.
The most violent seismic movements in history
This catastrophe does not take into account social classes, nor does it give much advance warning of when it will occur; so much so that its consequences can often be atrocious, devastating entire regions and countries, with the consequent deaths of their inhabitants.
Throughout the history of mankind, countless earthquakes have occurred, among the strongest are the following:
- Japan earthquake of March 2011 : it is undoubtedly the strongest in history and reached 8.9 on the Richter scale.
- Valparaíso (Chile) earthquake of July 1730 : one of the most serious earthquakes suffered in this country, which, like the last one in Japan, was followed by a tsunami that devastated several kilometres of the coast. The earthquake reached 8.7 on the Richter scale and the tsunami waves were 14 metres high.
- Lisbon earthquake (Portugal) in November 1755 : this was an earthquake that measured almost 8.7 on the Richter scale ; it was a time of great tension, especially because it was not only accompanied by a tsunami but also by major fires. In total, more than 10,000 people died.
- Rat Island earthquake (Alaska) in February 1965 : This earthquake was also followed by a tsunami, with waves up to 10 metres high, which caused destruction along the coast. Traces of this earthquake were felt in all the countries of Central America, 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, among which were Panama, Mexico, Japan and Colombia.
- February 2010 Chile earthquake : This was the strongest earthquake to hit the country, measuring 8.8 on the Richter scale and claiming the lives of 521 people.