How we measure earthquakes - CNN

How earthquakes are measured

(CNN)Earthquakes are measured using seismographs, which monitor the seismic waves that travel through the Earth after an earthquake strikes.

Scientists used the Richter Scale for many years but now largely follow the "moment magnitude scale," which the U.S. Geological Survey says is a more accurate measure of size.
Here are the magnitude classes:
    Microearthquake:
      -- Magnitude: Less than 3.0
      -- Damage: Little to none
      Minor earthquake:
        -- Magnitude: 3.0 - 3.9
        -- Damage: Little to none
        Light earthquake:
        -- Magnitude: 4.0 - 4.9
        -- Damage: Moderate
        Moderate earthquake:
        -- Magnitude: 5.0 - 5.9
        -- Damage: Considerable
        Strong earthquake:
        -- Magnitude: 6.0 - 6.9
        -- Damage: Severe
        Major earthquake:
        -- Magnitude: 7.0 - 7.9
        -- Damage: Widespread, heavy
        Great earthquake:
          -- Magnitude: 8.0 and up
          -- Damage: Tremendous