After the biggest earthquake to hit Southern California in 20 years struck in July, a powerful fault line that could cause a magnitude 8 earthquake began moving, scientists say.

In a study published Thursday in the journal Science, researchers from the California Institute of Technology along with NASA’s Jet Propulsion Laboratory said a part of the Garlock fault slipped after being triggered by the series of earthquakes in the Ridgecrest area. The fault runs 185 miles east to west from the San Andreas Fault to Death Valley. Scientists found that it has slipped 0.8 inch (or about 2 centimeters) near its surface since July.

Researchers were able to record the movement for the first time through satellite imagery and seismometer data. The discovery marks the firs…