How do Scientists Measure the Magnitude of Tectonic Events?

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  • Measuring Tectonic Events
    • Modified Mercalli Scale
      • Measures the destructiveness of an earthquake. 
      • It is a relative scale as people would feel different amounts of shaking in different places.
      • It subjective as based on if people wake up, if furniture moves, how much damaged structures receive.
      • The scale varies from I to XII I = Generally not felt by detected on seismographs XII = Nearly total destruction
      • It doesn’t consider economic, social and environmental impacts.
    • Moment Magnitude Scale (MMS)
      • Measures the amount of energy released in earthquake.
      • Scale from 0-9.
      • It's a simple measure, so environmental or social impacts must be inferred.
    • Volcanic Explosivity Index (VEI)
      • Measures the relative explosiveness of a volcanic eruption.  
      • Based on the height of ejected material and duration of eruption.
      • Scale goes from 0-8 and is logarithmic (increase of 1 on the scale indicated a 10 times more powerful eruption).
    • Richter Scale
      • Measures the amplitude of the waves produces during an earthquake
      • Most widely used scale, as it's absolute
      • Must infer social or environmental impacts, which can be misleading. The highest Richter scale earthquake readings won't necessarily be the worst disasters.
      •  Like the VEI its scale is logarithmic.


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