Do Now

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Do Now In Notebooks

1. What is an earthquake?
2. What kind of stress acts on a normal fault? Does
   the crust lengthen or shorten?
3. What is the difference between the focus and
   epicenter of an earthquake?

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Measuring Earthquakes
How are earthquakes measured?
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Seismology

• The study of earthquake waves is called
  Seismology
• Earthquake waves can be detected at great
  distances by Seismometers
• A seismometers record is known as a Seismogram

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Time-Travel Curves

• Years of data collection has led to time-travel
  curves
• The curves tell the time an S- and P-wave takes
  to reach a certain distance
• P-waves arrive first
• The difference between waves on a seismogram
  determines the distance from the epicenter

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Time-Travel Curves
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Locating Earthquakes

• Epicenters are located by the separation between
  S- and P-waves on a seismogram
• Cannot use one location to map epicenter
• Need to use three or more seismic stations
• Time can be measured in same way

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Magnitude and Intensity

• The amount of energy released during an
  earthquake is known as its magnitude
• The amount of damage done by an earthquake is
  known as intensity
• Three scales measuring intensity/magnitude
• Richter Scale
• Moment Magnitude Scale
• Modified Mercalli Scale

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Do Now In Notebooks

• What is the difference between an earthquakes
  magnitude and intensity?
• What is the amplitude of a curve?
• You will need
• Notebooks
• Southern California Earthquake Packet
• Pencil
• Calculator (See me if you need one)

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Magnitude and Intensity

• How are earthquakes measured?

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Richter Scale - Magnitude

• The Richter Scale is based on the largest waves
  generated by the quake
• Each number on the scale is an increase of 10
• Ex 8 is 10x larger than 7, 100x larger than 6

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Moment Magnitude Scale

• The Moment Magnitude Scale includes
• Size of fault rupture
• Amount of movement along fault
• Rocks stiffness
• Uses more data than Richter Scale More accurate

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Modified Mercalli Scale - Intensity

• The Modified Mercalli Scale assesses damage from
  a quake

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Factors affecting Intensity

• Depth of Focus
• Distance from Epicenter