EarthQuake

EarthQuake :

1) Definition
2) Characteristic of the phenomenon
3) different types of earthquakes
4) Example of the most devastating earthquakes.

I) Definition:

An earthquake is a shake of the ground resulting from the sudden release of energy accumulated by the stresses exerted on the rocks. This release of energy occurs by breaking along a fault, usually pre-existing. More rare are earthquakes due to volcanic activity or artificial origin (explosions for example). The place of the rupture of the rocks at depth is called the hearth; the projection of the focus to the surface is the epicenter of the earthquake. The movement of rocks near the focus generates elastic vibrations that propagate in the form of seismic wave trains around and across the globe. It also produces heat by friction, sometimes melting the rocks along the fault

2) Characteristic of the phenomenon

The hypocenter or seismic focus may be between the surface and up to seven hundred kilometers of depth (upper mantle boundary) for the deepest events.
The three main types of flaws
Four categories of earthquakes
An earthquake is a more or less violent earthquake that can have four origins: breaking a fault or fault segment (tectonic earthquakes); intrusion and degassing of a magma (volcanic earthquakes); "Crunches" of the ice caps reverberating in the earth's crust; explosion, collapse of a cavity (earthquakes of natural or human origin) In practice, earthquakes are classified into four categories according to the phenomena that generated them:

Tectonic earthquakes
Earthquakes of Volcanic Origin
Earthquakes of Polar Origin
Earthquakes of artificial origin

3) Different types of earthquakes

a) The Tectonic earthquakes:

Tectonic earthquakes are by far the most frequent and devastating. A large part of the tectonic earthquakes occurs at the boundaries of the plates, where a sliding occurs between two rocky environments. Another part takes place along an existing or newly developed fragility plan. This sliding, located on one or several faults, is blocked during the inter-seismic (seismic) periods of seismic displacement of the two blocks separated by the potential rupture zone (the fault is then inactive) accumulates by the elastic deformation of the rocks

b) The earthquakes of Volcanic Origin

Earthquakes of volcanic origin result from the accumulation of magma in the magmatic chamber of a volcano. The seismographs then record a multitude of micro-earthquakes (tremor) due to ruptures in the compressed rocks or the degassing of the magma3. The progressive rise of the hypocenters (linked to the rise of the magma) is an indication that the volcano is in the awakening phase and that an eruption is imminent

c) The Earthquakes of Polar Origin

Glaciers and the ice layer have some elasticity, but the differentiated and periodic advances (marked seasonal rhythm) of ice flows cause fractures whose elastic waves generate earthquakes, recorded by seismographs far from the pole across the ice world

d) The Earthquakes of artificial Origin

Earthquakes of artificial origin or "earthquakes" of low to medium magnitude are due to certain human activities such as dams, deep pumping, mining, underground or nuclear explosions, or even bombardments

4) Example of the most devastating earthquakes.

(Name, magnitude , date , dead people , hurt people , comment )

-Chile Chile Valdivia in the Rivers Region 9.5 May 22, 1960 3,000 Valdivia's 1960 earthquake (the most violent earthquake ever recorded)

-Indonesia Indonesia Andaman Islands 9.4 26 December 2004 227 898 125 000 Earthquake of 26 December 2004 in the Indian Ocean

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