Earthquakes

The study of earthquakes is called seismology. The study of the earth is called geology.

Put simply, earthquakes are the shaking, rolling or sudden shock or vibration of the earth’s surface by breaking rock. A natural means of releasing stress.

**There is a limit of how far something can bend and stretch, which is the elastic limit.**


 * Buckling **
 * and **
 * Bending **
 * of Rocks can Occur **


 * Once this limit is passed, the rocks will break. **

During an earthquake, the 2 blocks of earth can suddenly slip past one another. The surface where they slip is called the: //fault// or // fault plane //. The location below the earth’s surface where the earthquake starts (the underground origin of the earthquake) is called the... //hypocenter (or focus)// and the location directly above the hypocenter on the surface of the earth is called the... epicenter

The type of earthquake depends on the region where it occurs and the geological make-up of that region. Tectonic Earthquakes **(Most Common)** These occur when rocks in the earth's crust break due to geological forces created by movement of tectonic plates.

Volcanic Earthquakes These occur in conjunction with volcanic activity.

Collapse Earthquakes These are small earthquakes in underground caverns and mines.

Explosive Earthquakes These result from the explosion of nuclear and chemical devices.

Tension The force that pulls rocks apart.

Compression The forces that squeezes rocks together.

<span style="color: #0000ff; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 120%; text-align: center;">Shear The forces that causes rocks on either side of a fault to slide past each other

<span style="color: #0000ff; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 120%; text-align: center;">Normal Faults The force of tension moving rock above the fault downwards in relation to the rock below

<span style="color: #0000ff; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 120%; text-align: center;">Reverse Faults The force of compression that squeezes rock from opposite directions, the rock surface is forced up and over the rock below the fault surface.

<span style="color: #0000ff; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 120%; text-align: center;">Strike-Slip Faults The forces on either sides of the faults that are moving past each other.

<span style="color: #800000; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 117%; text-align: center;">Lets see if you can guess which type of fault is seen in the pictures below! <span style="color: #800000; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 90%; text-align: center;">(highlight below the pic to find the answer)

<span style="color: #ffffff; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 117%; text-align: center;">Reverse Fault

Slip Fault



<span style="color: #ffffff; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 140%; text-align: center;">**Normal Fault** Between certain regions of tension in Normal Faults there are sometimes individual blocks made by the faulting. A __**horst**__ represents a block pushed upward. and a //**graben**// is a block that has dropped. <span style="color: #0053ff; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 140%; text-align: center;">When the rocks move past each other along faults, they create stress points. Areas of the rocks' irregular surfaces catch each other. The stress continues to build up until the elastic limit is exceeded and energy is released in the form of... <span style="color: #0000ff; display: block; font-family: 'Comic Sans MS',cursive; font-size: 130%; text-align: center;">**__Seismic Waves__** are earthquake waves <span style="color: #000080; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 120%; text-align: center;">There are 3 types: <span style="display: block; font-family: 'Comic Sans MS',cursive; text-align: center;"> <span style="color: #800000; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 120%; text-align: center;">Primary Waves (P-waves) <span style="display: block; font-family: 'Comic Sans MS',cursive; text-align: center;">Fastest type of wave. Causes a back and forth motion in the direction the wave is traveling. Will pass through solid, liquid and gas. <span style="color: #0053ff; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 140%; text-align: center;">

<span style="color: #800000; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 120%; text-align: center;">Secondary Waves (S-waves) <span style="display: block; font-family: 'Comic Sans MS',cursive; text-align: center;">Causes rocks to move in right angles to the direction the wave is traveling. Second Fastest wave. Will only travel through solids. Will NOT pass through liquids and gases; creating a __**shadow zone**__. <span style="color: #800000; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 120%; text-align: center;"> Surface Waves (L-waves) <span style="display: block; font-family: 'Comic Sans MS',cursive; text-align: center;">Slowest moving seismic waves that will arrives last. Causes a backward, rolling motion. The most destructive waves

<span style="display: block; font-family: 'Comic Sans MS',cursive; font-size: 130%; text-align: center;">[|Try this Fun Review Game]

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**__The Origin of Seismic Waves__** ==

The point beneath the Earth's surface where the energy is released when the rocks break and move thus exceeding the elastic limit. This describes the...
<span style="display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 130%; text-align: center;">Some Terms to Know: **__Seismograph__** – is an instrument that detects and measures seismic waves. For every 1 point rise 30 times the energy is released. <span style="color: #000080; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 169%; text-align: center;">__**Richter Scale**__ <span style="color: #000080; display: block; font-family: 'Arial Black',Gadget,sans-serif; font-size: 130%; text-align: center;">4 - Minor Earthquake 5 - Moderate Earthquake 6 - Strong Earthquake 7 - Major Earthquake 8 - Great Earthquake __**Magnitude**__ - The height of a line traced on a seismogram.
 * __Seismogram__** – is the record of waves. (paper record)
 * __Seismologists__** – scientists who study earthquakes. **__Seismograph Stations-__**way for identifying the epicenter of the earthquake through triangulation
 * __Richter scale__** – calculation of the strength or magnitude of an earthquake.

<span style="color: #ff0000; display: block; font-family: 'Palatino Linotype','Book Antiqua',Palatino,serif; font-size: 156%; text-align: center;">**__Liquefaction__** – Shaking up of wet soil making it unstable. This causes surface object to sink. <span style="color: #0000ff; display: block; font-family: 'Palatino Linotype','Book Antiqua',Palatino,serif; font-size: 140%; text-align: center;">**__Tsunamis__ – A giant sea wave produced by an earthquake.** [|Tsunamis Animation]

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