Big Temblor Is Followed by Worst Quake in 20 Years

A quake with a magnitude as large as 7.1 jolted much of California, cracked buildings, set fires, broke roads, and caused several injuries, authorities and residents say. The quake—preceded by Thursday's 6.4 magnitude temblor in the Mojave Desert—was the largest Southern California temblor in at least 20 years and was followed by a series of large and small aftershocks. It hit at 8:19pm local time and was centered 11 miles from Ridgecrest, in the same areas where the previous quake hit, but it was felt as far north as Sacramento, as far east as Las Vegas, and as far south as Mexico. Early magnitude estimates from the US Geological Survey wavered between 6.9 and 7.1. A rep for the Kern County Fire Department says there were reports of multiple injuries and multiple fires. For more:

• The odds: "You know we say we [have a] 1 in 20 chance that an earthquake will be followed by something bigger? This is that 1 in 20 time," tweeted Lucy Jones, a seismologist at Caltech. She adds there have been over a thousand aftershocks since the Thursday quake, per CBS News, and there's about a 1-in-10 chance another 7.0 quake could hit within the next week; the chance of a 5.0-magnitude quake "is approaching certainty," she says.

• The science: The increased risk is based on a simple fact: earthquakes increase the chance for more earthquakes, the LA Times explains. But the "Big One" is unlikely to occur because the San Andreas fault is a distant 100 miles away.
• On video: Viral videos of the Friday quake include shaking in the Los Angeles Dodgers press box (the players kept playing) and merchandise falling from the shelves in local businesses, Newsweek reports. Another video shows news anchors hiding under their desk.
• The governor: California Gov. Gavin Newsom declared a state of emergency after the second temblor, CNN reports. "The state is coordinating mutual aid to local first responders," he tweeted.
• Trona: The worst-hit town is Trona, which is 20 miles northeast of Ridgecrest, per the Sacramento Bee. Officials say broken roads make it hard to reach its 1,500 residents, and there's concern about the Searles Valley Minerals plant, which manufactures borax materials and other compounds in the town.
• Health care: Patients at Ridgecrest Regional Hospital were wheeled outside after the Friday quake and tended to by nurses in the dark, CNN reports. Some were still hooked to IVs.
• The future: The current earthquake sequence will likely last a while: "Years, probably," says the LA Times.

(More earthquake stories.)