Causes and effects of Earthquake.

Earthquake

An earthquake is a shaking movement of the surface of the Earth. Big earthquakes usually begin with slight tremors rapidly increasing to one or more violent shocks followed by several less severe after shocks. Earthquakes occur along fault lines (cracks in the Earth's crust). The crust is segmented into giant plates of rock. Sometimes two plates scrape together and one gets caught on the other. Pressure increases until the plates snap into a new position. The release of pressure causes vibrations that we feel as an earthquake. An earthquake's origin deep in the Earth is called the focus; the point on the Earth's surface directly above the focus is the epicenter. There are two types of earthquake vibrations, or "seismic waves". One type of surface wave, travels along the earth's surface, usually has the strongest vibrations and causes most of the damage near the epicenter. The second type, called body waves, move faster, and travel through the Earth from the focus to distant points on the earth's surface. Primary (compressional) body waves reach the Earth's surface first. They can travel through all layers, and particles of rock move back and forth in the same direction as the waves. Secondary (shear) body waves travel about half as fast as primary waves and reach the Earth's surface after primary waves. Secondary waves cannot travel through liquid layers in the Earth; rock particles move at right angles to the direction of the secondary waves.

Seismologists measure the strength of an earthquake by estimating the amount of energy released at the focus. Seismic waves are detected, recorded, and measured by sensitive instrument called "seismographs".

The effects of an earthquake
The effects of an earthquake are terrible and devastating... The environmental effects of it are that including surface faulting, tectonic uplift and subsidence, tsunamis, soil liquefaction, ground resonance, landslides and ground failure, either directly linked to a quake source or provoked by the ground shaking.

 There are four different types of earthquakes: Tectonic, volcanic, collapse and explosion. A tectonic earthquake is one that occurs when the earth's crust breaks due to geological forces on rocks and adjoining plates that cause physical and chemical changes.

• A tectonic earthquake is one that occurs when the earth's crust breaks due to geological forces on rocks and adjoining plates that cause physical and chemical changes.

• A volcanic earthquake is any earthquake that results from tectonic forces which occur in conjunction with volcanic activity.

• A collapse earthquake are small earthquakes in underground caverns and mines that are caused by seismic waves produced from the explosion of rock on the surface.

• An explosion earthquake is an earthquake that is the result of the detonation of a nuclear and/or chemical device.