Earthquakes along the san andreas fault zone, for example, are repetitive—they reoccur in roughly the same regions over and over again—separated by decades or centuries because earthquakes along the san andreas fault zone, for example, are repetitive—they reoccur in roughly the same regions over and over again—separated by decades or centuries because faults are always moving or creeping so an earthquake will occur whenever two sides meet that have the right properties for an earthquake there are areas that are weak and always break when small amounts of energy are applied to them plate boundaries move at regular rates so the interactions across plate boundaries are predictable and regular