Original: Amos Nur postulates that earthquakes tend to occur in "sequences" or "storms" where a major earthquake above 6.5 on the Richter magnitude scale can in later months or years set off second or subsequent earthquakes along the weakened fault line.
Simplified: Earthquakes tend to occur in sequences or 'storms', where a major earthquake above 6.5 on the Richter magnitude scale can set off later earthquakes along the weakened fault line.