Earthquake Essay | An Essay on Earthquake | Earthquakes | Earthquake

The recent earthquake In India on September 18 , 2011 compelled me to write an essay about earthquake. In this essay many things related to earthquake will be discussed.

Definition:

An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves.The seismicity or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time.

Measurement:

Earthquakes are measured with the help of  seismometers. The moment magnitude is the most common scale on which earthquakes larger than approximately 5 are reported for the entire globe. The more numerous earthquakes smaller than magnitude 5 reported by national seismological observatories are measured mostly on the local magnitude scale, also referred to as the Richter scale. 

Magnitude of concern:

Magnitude of 3 or lower earthquakes are mostly almost imperceptible and magnitude 7 and over potentially cause serious damage over large areas. The largest earthquakes in historic times have been of magnitude slightly over 9. But  there is no limit to the possible magnitude. The most recent large earthquake of magnitude 9.0 or larger was a 9.0 magnitude earthquake in Japan in March 2011. It was the largest Japanese earthquake since records began. Intensity of shaking is measured on the modified Mercalli scale. 

Cause:

Earthquakes are caused mostly by rupture of geological faults. It is  also cause by other events such as volcanic activity, landslides, mine blasts, and nuclear tests. An earthquake's point of initial rupture is called its focus or hypocenter. The epicenter is the point at ground level directly above the hypocenter.