How Erthquake Happens

       Earthquake is one of the most destroying natural disasters. Unluckily it often happens in several regions. Recently a horrible earthquake has shaken West Sumatra. It has brought great damages. Why did it occur? Do you know how an earthquake happens?

        An earthquake is the result of a sudden release energy in the Earth’s crust that creates seismic waves. Earthquakes are measured using observations from seismometers. Earthquakes can also trigger landslides, and occassionally volcanic activity. When two blocks of rock or two plates are rubbing against each other, they stick a little. They don't just slide smoothly. The rocks are still pushing against each other, but not moving. After a while, the rocks break because of all the pressure that's built up. When the rocks break, the earthquake occurs. During the earthquake and afterward, the plates or blocks of rock start moving, and they continue to move until they get stuck again.

Earthquakes are caused mostly by rupture or geological faults, but also by other events such 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.

       Eartquakes can cause effects, the effects are

Flood

Earthquakes may cause landslids to dam rivers which collapse and cause floods.

Human impacts

An earthquakes may cause injury and loss of life, road and bridge damage, general property damage, and collapse building. Earthquakes may bring desease and lack of basic necesilities.

 Tsunami

Tsunamis can also travel thousand of kilometers across open ocean and wreak destruction on far shores hours after earthquake that generated them.

Ordinarilly, subduction earthquakes under magnitude 7.5 on the Richter scale do not cause tsunamis, although some instances of this have been recorded.