By Trinidad Arroyo

Earthquakes

What is an earthquake ?

Elastic rebound theory This gradual accumulation and

release of stress and strain is now referred to as the "elastic rebound theory" of earthquakes. Most earthquakes are the result of the sudden elastic rebound of previously stored energy.

If a stretched rubber band is broken or cut, elastic energy stored in the rubber band during the stretching will suddenly be released. Similarly, the crust of the earth can gradually store elastic stress that is released suddenly during an earthquake.

What Is A Fault ? Fault is a break in

the Earth's crust caused by movement of rock. Also known as Tension, Compression, and shearing.Tension: Pulls apartCompression: Pushes togetherShearing: slides apart in opposite directions

What Is a the earthquakes focus?

The focus (more correctly termed the hypocenter) of an

earthquake is the point in the earth where the

earthquake rupture or fault movement actually occurred.

The point on the surface directly above the

hypocenter is known as the epicenter.

The Epicenter

o The epicenter is the point on the earth's surface vertically above the focus (or the hypocenter) , point in the crust where a seismic rupture begins

Aftershock

A smaller earthquake following the main shock of a large earthquake

P-Waves the P waves which is

known as the (primary or compression) waves are the first to arrive at the recording station, p waves are formed when matter in the rocks is pushed together by the earth's movement. they can travel through solids and liquids.

P-waves are faster then S-waves

S-waves

the S waves which is known as the (secondary )waves are the second waves to arrive at the recording station. this waves are also called the shear waves. these waves are formed by the sideways motion of matter, it can only travel through solids.

Intensity & Magnitude The following table gives intensities that are typically

observed at locations near the epicenter of

earthquakes of different magnitudes.

Magnitude Typical MaximumModified Mercalli Intensity

1.0 - 3.0 I

3.0 - 3.9 II - III

4.0 - 4.9 IV - V

5.0 - 5.9 VI - VII

6.0 - 6.9 VII - IX

7.0 and higher VIII or higher

Mercalli ScaleThe mercalli scale tells you how much

damage the earthquake caused and the level of the intensity it is.