A magnitude 4.2 earthquake jolted residents in Northern California on Wednesday, setting off a “ShakeAlert” across the region. The quake occurred near the small community of Isleton in Sacramento County around 9:30 a.m., according to the U.S. Geological Survey (USGS). Fortunately, no injuries or damages were reported in the immediate aftermath.
A 4.2 magnitude earthquake struck Wednesday morning in Sacramento County, according to preliminary data from the U.S. Geological Survey.
Chuck Bergson, the city manager of Isleton, disclosed that he felt some tremors at City Hall during the quake. He also mentioned that the levees along the Delta seemed intact. “There was nothing major with this one,” Bergson assured.
Coincidentally, the Earthquake occurred a day before the annual Great ShakeOut, a global drill to test emergency systems for earthquake preparedness. As part of this exercise, thousands of users of the MyShake app will receive an earthquake test alert on Thursday.
Adding a sense of historical significance, the Earthquake took place a day after the 34th anniversary of the Loma Prieta earthquake, which impacted the San Francisco Bay Area in 1989. The devastating event claimed the lives of 63 individuals and left nearly 3800 others injured, causing up to $10 billion in damage.
Residents in the suburbs of the San Francisco Bay Area, including Antioch, Concord, Fairfield, Martinez, Orinda, Danville, and even Berkeley, the home of the University of California, felt the tremors. Consequently, a “USGS ShakeAlert” notification was sent to potentially millions of individuals across Northern California, spanning from Sacramento and San Francisco to San Jose and Silicon Valley.
Good morning Northern CA. Did you feel the magnitude 4.1 earthquake about 2.5 miles southwest of Isleton at 9:29 am? The #ShakeAlert system was activated. See: https://t.co/9raIKrK1CL @Cal_OES @CAGeoSurvey pic.twitter.com/W3pDng40uB
— USGS ShakeAlert (@USGS_ShakeAlert) October 18, 2023
The alert message read, “Earthquake Detected! Drop, Cover, Hold on. Protect Yourself!” The USGS confirmed that any earthquake registering above 4.0 would trigger an alert. The quake briefly disrupted Bay Area Rapid Transit (BART) train services in the affected area.
Christine Goulet, the director of the USGS’ Earthquake Science Center in Los Angeles, noted that while the Earthquake didn’t cause any destruction, the alert managed to capture the attention of millions. She explained that preliminary magnitude estimates varied between 5.7 on the MyShake app and an initial report 4.6 on the USGS site.
Goulet clarified that the wider alert coverage was not a flaw but an intentional design aspect of the alert system. The system triggered a more comprehensive area alert by detecting a more significant portion of the initial shake. This, in turn, made the event seem more significant than it actually was.
“There is always a tradeoff between accuracy and speed,” Goulet explained. “The alert system is designed to reach as many people as quickly as possible. Waiting longer would reduce our response time.” She emphasized that earthquake season is a constant threat, unlike seasonal natural disasters such as wildfires or tropical storms. Goulet acknowledged that the alert may have startled more people than intended but stressed the importance of safety. “It’s better to be safe than sorry,” she concluded. “The alert aims to save lives by instructing people to drop, cover, hold on, and find a secure space.”
