An earthquake of magnitude 3.5 produced light shaking from its epicenter in Orange County on Wednesday morning.
The epicenter occurred in Anaheim Hills, close to the freeway interchange between highways 91 and 241. The earthquake hit at 5:06 a.m. and began just 2.4 miles underneath the surface, making it quite shallow.
Small earthquakes like Wednesday’s are typical for California.
Coincidentally, a USGS study is to be released Wednesday highlighting a lack of supersized earthquakes for California.
The study, written by USGS scientists Glenn Biasi and Kate Scharer in the journal Seismological Research Letters, says that the century between 1919 and 2018 is almost certainly the only 100-year period in the past 1,000 years where there have been no earthquakes strong enough to literally break the ground on three of California’s most dangerous faults — the San Andreas, San Jacinto and Hayward.
A key finding from a @USGS study to be released soon: it's been 100 years since a major, literally ground-breaking quake on three of the state's most dangerous faults. That's basically unheard of in the last 1,000 years. And at some point, experts say, that's going to change— Ron Lin (@ronlin) April 2, 2019
Those three faults are important because, as a group, they produce the most frequent earthquakes on the plate boundary between the North American and Pacific plates — the San Andreas, San Jacinto and Hayward. They are the ones seen as most likely to cause trouble in our lifetime.
Ordinarily, there are roughly three to four of these earthquakes on these faults every 100 years.
“The next century is unlikely to be as quiet as this one. It’s hard to beat,” said Biasi, the lead author of the study.
The 1800s, by comparison, were far more active for earthquakes. That century saw six large temblors on this trio of faults; between 1800 and 1918, there were eight. That’s an average of one major quake on those faults every 16 years.
Earthquake scientists have been buzzing for years about California’s hiatus in supersized earthquakes, thinking the chances of such a 100-year gap between ground-shattering seismic events to be improbable. “Did Someone Forget to Pay the Earthquake Bill?” was the title of a talk by UCLA geophysicist David Jackson at the Seismological Society of America conference in 2014.
Scientists focus on earthquakes that literally break the ground along the main plate boundary because they’re the ones that actually do the job of relieving centuries of tectonic strain. A famous example of the ground breaking was during the great 1906 earthquake that destroyed much of San Francisco; at Point Reyes in Marin County, a fence that intersected the fault was suddenly cut in two, separated on each side of the San Andreas by 18 feet.
Read more about the study on California’s earthquake drought.