Monday, 13 May 2013

Something about Earthquakes

The rattling windows, the shattering glass panes, the trembling ground – when all these events occur together we call it an 'Earthquake'. But few Humans out there doesn't really know (or they are least cared) about how these things happen. If you belong to the 'least bothered' category, this article might sound interesting and if you know the facts then this could serve as a quick refresh.

Earthquakes occur due to the collision of tectonic plates beneath the Earth surface. To know something about Earthquakes, first of all we should understand what tectonic plates are. The Earth's outer layer is broken into pieces and those pieces are called tectonic plates. These plates are about 100 km thick and they are constantly in motion. The edges of these tectonic plates are called the plate boundaries. The plate boundaries are made up of many faults and most of the earthquakes occur on these faults. The location below the Earth's surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the Earth is called the epicenter.

When the tectonic plates are in motion, the edge of the plates which are rough gets stuck as they bump into each other. This ceases the motion of the plate edges while the rest of the plate is still moving. In this case, the energy that would normally cause the plates to move is stored up in the edges. Finally, when the plate has moved far enough, it unsticks the edges and all the energy stored in the edges are now released on to the Earth's surface. The energy radiates outward like the seismic waves. These waves shake the Earth as they move through it and when they reach the surface, they shake the ground and anything on it (buildings, mountains, trees, etc). Hence the definition goes like – Earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves (refer Wikipedia for the definition).

Sometimes the earthquake has foreshocks. The foreshocks are the smaller earthquakes happen in the same place where the larger earthquake follows. The larger earthquake is called the mainshock. Sometimes there are smaller earthquakes that occur after the mainshock. These are called aftershocks. If the intensity of any aftershock is greater than the mainshock, then the greater antishock is converted into the mainshock and the previous mainshock becomes a foreshock. If the Earthquake occurs in the sea bed, it gives rise to a gigantic wave called 'Tsunami'.  

Tectonic plates around the globe