Measuring Earthquakes 2.2


Focus: the point beneath Earth's surface where rock that is under stress, breaks, triggering an earthquake.
Epicenter: the point on the surface directly above the focus.
Seismic waves: vibrations the travel through Earth carrying the energy released during an earthquake.
P Waves: earthquake waves that compress and expand the ground like an accordian.
S Waves: earthquake waves that vibrate from side to side as well as up and down.
Seismograph: records the ground movements caused by seismic waves as they move through the Earth.
Magnitude: a measurement of earthquake strength based on seismic waves and movement along the faults.
Surface waves: move slower than S and P waves, but produces the most severe ground movements.
Mercalli Scale: developed to rate earthquakes according to their intensity.
Richter Scale: a rating of the size of seismic waves as measured by a particular type of mechanical seismograph.
Moment-magnitude scale: a rating system that estimates the total energy released by an earthquake.


  • Measuring Earthquakes

      • focus
      • epicenter
  • Seismic Waves

      • seismic waves
      • seismic waves carry energy from earthquakes
      • three seismic waves- P waves, S waves, surface waves
    • Primary waves
      • P waves
    • Secondary Waves
      • S waves
    • Surface waves
      • surface waves
  • Detecting Seismic Waves

      • seismograph
  • Measuring Earthquakes

      • magnitude
    • Mercalli Scale
      • mercalli scale
    • Richter Scale
      • richter scale
    • The moment magnitude scale
      • moment magnitude scale
  • Locating the epicenter

      • use seismic waves to locate epicenter