EARTHQUAKE

Recently, all of us read in the newspapers and watched on T.V.'s the severe earthquake caused in Pakistan and Jammu Kashmir. So, here is a note on earthquake.

An earthquake occurs when the structure of the earth shifts and moves. One of the causes is due to the movement of molten rock down in the earth's crust. The rocks become soft when they are exposed to great heat of the interior earth, and this change makes them move. Because of this movement beneath, we on the surface, feel that the ground is shaking. It is called the earthquake. The volcanic eruptions also cause earthquakes.

The place of the origin of earthquake is called as Epicentre and the point at which an earthquake occurs is called Focus or Hypocentre. The regions which are proned to earthquake are called Seismic belt.

There are two kinds of earthquake volcanic and tectonic. They are measured using the Richter scale devised by C.F. Richter. And there are three types of earthquake Shallow, Intermediate, and Deep.

There are some man made causes for the earthquakes like filling of very large dams, direct injection of fluids into the ground, underground nuclear explosions, etc.

The worst earthquake disaster ever recorded so far is in the shensi, Shansi, and Honan provinces of China on Feb 2nd, 1556 which is estimated to have killed more than 8,30,000 prople.
Mercalli scale is used to access the effects of a quake qt a particular place.