Year after year, nothing happened.When a quake did finally hit on September 28, 2004, it was years off schedule, but most disappointing was the lack of warning signs.Scientists reviewed the data but could find no evidence of anything unusual preceding the September 28th quake.It led many to believe that perhaps earthquakes really are random events.Instead of giving up, though, scientists in Parkfield dug deeper into the ground.By late summer 2005, they had reached the fault's final depth of three kilometers (two miles), where they continued collecting data, hopping to find a clue.