Living through almost a year of the pandemic and the worst wildfire season on record in California has a lot of Bay Area residents on edge.
And, more recently, several small earthquakes have jolted the Bay Area, including a 3.9 magnitude quake Sunday near Gilroy, and others in Berkeley, Concord and Aromas.
The temblors caused no significant damage but perhaps rattled some nerves and raised concerns: Could a bigger event be on the way?
Experts said we shouldn’t get too worried — but we also shouldn’t let our guard down.
“Earthquakes are literally happening all the time, and most of them are so microscopic we don’t even feel them,” said Sarah Minson, a research geophysicist at the U.S. Geological Survey.
Dr. Angela Chung, a project scientist for Earthquake Early Warning at the Berkeley Seismological Laboratory, said that overall, earthquake activity has actually been pretty quiet in the Bay Area.
“This was very normal activity and nothing that concerns me at all,” she said.
People can sign up for emergency apps including MyShake, which sends ShakeAlert earthquake warnings.
Michael Short / Special To The ChronicleThe largest of these recent events was a 4.2 magnitude earthquake on Jan. 16 in Monterey County near Aromas, which was felt by residents in San Francisco, the East Bay and Marin County. Chung said the quake was definitely felt, but not large enough to trigger the earthquake warning system.
Chung added that these small earthquakes do not necessarily mean a larger event is on the way. There aren’t any really reliable indicators to predict quakes — except that a moderate to larger earthquake has a 20% chance of leading to a large earthquake.
A recent example was the 2019 Ridgecrest Earthquake Sequence. On July 4, 2019, a series of foreshocks occurred over the course of an hour near the Kern County town of Ridgecrest in Southern California. Then, a magnitude 6.4 quake hit that could be felt in Northern California and Phoenix.
Hundreds of aftershocks followed, and 34 hours later, a 7.1 magnitude earthquake hit.
Earthquakes that occur in the Bay Area happen on two main faults:
• The San Andreas Fault system is more than 800 miles long, and in Northern California, it runs through the Santa Cruz Mountains to the San Francisco Peninsula. It was responsible for the magnitude 6.9 Loma Prieta Earthquake in 1989.
• On the east side of the bay is the Hayward Fault, which runs about 74 miles. The largest quake recorded on the fault was a magnitude 6.8 that occurred in 1868.
While the recent events are not particularly worrisome to experts, Chung said they’re a good reminder to be prepared. People should practice “drop, cover and hold on” drills, and make an emergency plan.
“Especially with the pandemic now, it’s really, really important that people are prepared,” Chung said. “Having some kind of backup plan is important.”
A major event could force people to survive without power, water or shelter for several days or longer, so building a disaster kit is important. Chung said people should try to stock up with a two-week supply of nonperishable food and water. Other important items include a fire extinguisher, medicine, first aid kid, flashlight, hand sanitizer, face masks, hand-crank radio, extra batteries and a whistle.
“After big earthquakes, pretty typical things that go out are the power, the water mains get broken, which is why you want to have water available, and the gas mains sometimes get turned off to prevent leaks,” she said.
People can also sign up for emergency apps including MyShake, which sends ShakeAlert earthquake warnings. The American Red Cross has an app specifically for earthquakes.
Minson said people should be ready for both a larger or smaller event.
“You can get significant shaking even from little earthquakes,” she said. “You want to make sure your house is ready for that.”
This means securing heavy items including bookcases, televisions, appliances and objects on the walls, making structural improvements to your home to prevent collapse, and ensuring heavy or valuable items are stored on lower shelves, according to Ready.gov.
Kellie Hwang is a San Francisco Chronicle staff writer. Email: kellie.hwang@sfchronicle.com Twitter: @KellieHwang
February 24, 2021 at 07:03PM
https://www.sfchronicle.com/bayarea/article/About-all-these-recent-little-earthquakes-in-the-15974500.php
About all these recent little earthquakes in the Bay Area: Should we be worried? - San Francisco Chronicle
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