(CNN)The Ridgecrest earthquake in July was the strongest to strike Southern California in 20 years. And the main quake, along with more than 100,000 aftershocks, caused a major fault to move for the first time, researchers say.

The movement attributed to the quake is less than an inch along the surface of the fault and would be virtually undetectable to an ordinary resident. But it has intrigued researchers for two reasons. They’re not clear what it means,