Earthquakes are caused when underground rock along a fault line suddenly slip/break, causing rapid motion along the fault.

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This sudden release of energy creates seismic waves. Seismic waves spread out in every direction and cause the ground to shake.

​Earthquakes

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• ​Slower moving waves

• Only move through solids (Earth's crust)​

• Move the ground up and down ​or side-to-side (create the shaking feeling)

​S - Waves:

• ​Fast moving waves

• Move through solids, liquids, & gases

• Move in a coiled pattern causing a spring-like motion

​P - Waves:

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​Earthquakes create two types of seismic waves

The focus is the point inside the Earth's crust where the earthquake originated from.

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​Focus & Epicenter

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​The epicenter i​s the point above Earth's crust where the earthquake originated from. The Epicenter is directly above the focus!

Seismologists use the process of triangulation to determine the epicenter of an earthquake. 

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Seismologists first determine when P-waves arrive to a seismograph. They then will count how long it takes for the S-waves to arrive to the same seismograph. Scientists then take this data from 3 seismographs and put it together to find the epicenter. The longer it takes the S-waves to arrive, the farther away the epicenter of the earthquake is from a seismograph

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​Triangulation

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​The Richter Scale

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​Measures the magnitude of an earthquake

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The magnitude is the maximum motion/energy of an earthquake

​Moment of Magnitude Scale: 

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​Measures the total amount of energy released 

​The Modified Mercalli Scale:

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​Uses roman numerals to express intensity (damage to surfaces) of an earthquake