Measuring Earthquakes

• Richter scale


  Measure of the magnitude (strength) of an earthquake
• Richter scale developed


  1935
• Determining earthquake magnitude using Richter scale


  Measure amplitude of seismic waves
• Richter scale


  • Logarithmic scale
  • Each whole number increase represents a tenfold increase in amplitude of seismic waves
  • Represents a 30 fold increase in energy released
• The Richter scale has no upper limit
• The greatest earthquake recorded was a 9.5 magnitude in Chile 1960
• Moment magnitude scale


  Measures the energy released by an earthquake more accurately than the Richter scale
• Moment magnitude scale


  • The amount of energy released is related to the geological properties such as rock rigidity, area of the fault surface and the amount of movement in the fault
  • It is not used for small earthquakes
• Modified Mercalli scale


  Measures the intensity of the damage caused after an earthquake
• Modified Mercalli scale


  • It relates to the ground movement to impacts that can be felt and seen to anyone in the affected location
  • It is a qualitative assessment based on observation and description and is therefore subjective
  • It is a 12 point scale (I-XII)