
 Earthquake  MSN Encarta 
  The Richter scale measures the amplitude, or height, of seismic surface waves. 
  Seismologists calculate moment magnitude by measuring the seismic moment of an earthquake, or the earthquake’s strength based on a calculation of the area and the amount of displacement in the slip. 
  The moment magnitude of the 1906 San Francisco earthquake was 7.6; the Alaskan earthquake of 1964, about 9.0; and the 1995 Kōbe, Japan, earthquake was a 7.0 moment magnitude; in comparison, the Richter magnitudes were 8.3, 9.2, and 6.8, respectively for these tremors. 
 encarta.msn.com /encyclopedia_761571674_5/Earthquake.html (2048 words) 
