Earthquakes

1
Earthquakes

• Measuring Earthquake Magnitude
• Seismometer
• A mass suspended between two springs.
• When the earth moves the mass stays still, so the
  container moves relative to the mass.

2
Earthquakes
3
Earthquakes

• In modern seismometers, the mass is actually a
  magnet inside a coil.
• When it moves it induces a current in the coil
  which is amplified and transported many km away
  to the main station.

4
Earthquakes
(a seismograph is a seismometer connected to the
contraption that draws the seismogram)
5
Earthquakes
Two scales are used to measure earthquakes
Mercalli scale
Based on intensity, i.e. an assessment of
damage or other observable effects at a
particular location
Richter scale
Measures the amplitude of seismic waves. i.e.
measures the amount of energy released
(see handouts for descriptions of each scale)
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Earthquakes

• Richter scale is logarithmic.
• 7.0 is 10 times stronger than 6.0
• 8.0 is 10 times stronger than 7.0
• etc
• Therefore 8.0 is 100 times stronger than 6.0.

• Question
• An 8.0 earthquake on the Richter scale releases
  ___________ times as much energy as a 2.0
  earthquake.

1000000
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Assignment

• Classwork
• Read pages 295 296
• Page 296, Review 13.4,
• Questions 1-6

• Homework
• Page 290, Review 13.2,
• Questions 1-6