The quake, centered 11 miles from Ridgecrest area, was originally listed as a 7.1 and was downgraded shortly after.
There are no immediate reports of damage or injuries.
Seismologist Dr. Lucy Jones said the 6.4 is now a foreshock, and the new, larger quake was on the same fault and part of the same sequence.
So the M6.4 was a foreshock. This was a M7.1 on the same fault as has been producing the Searles Valley sequence. This is part of the same sequence –
— Dr. Lucy Jones (@DrLucyJones) July 6, 2019
People reported feeling the earthquake in areas as far as San Francisco and Las Vegas. The quake was felt downtown as a rolling motion that seemed to last at least a half-minute.
The U.S. Geological Survey says it also was felt in Mexico.
If the preliminary magnitude is correct, it would be the largest Southern California quake in 20 years.
