The United States Geological Survey (USGS) recorded a relatively mild tremor Sunday late afternoon at 4:02 p.m. in the Bay Area, with light shaking felt across San Leandro — and even as far north as Vallejo.
Between today's earlier 3.5-magnitude earthquake observed in SoCal and the Bay Area's most recent rattling this afternoon, Earthquake Twitter had a field day. Thankfully though, Sunday's 3.2-magnitude earthquake that shook the East Bay was quite mild and likely caused no structural damage, whatsoever.
We celebrate Waverly J. Person, Army veteran, civil rights activist and coined the Nation’s first black earthquake seismologist. Known by many as "Mr. Earthquake," Waverly helped establish the USGS National Earthquake Information Center. #BlackHistoryMonth pic.twitter.com/UCVd4XbzVK— USGS (@USGS) February 3, 2022
The East Bay tremor, itself, occurred along the Hayward Fault line, which runs from San Pablo Bay to south of Fremont, passing through other East Bay cities like Berkeley, Oakland, and Hayward. The fault that sits south of Fremont actually branches into a complex set of less distinct surface faults, all of which connect the Hayward Fault to the central part of the Calaveras Fault — an 80-mile-long tectonic strike-and-slip fault line that runs throughout much of the South Bay.
Geologic studies conducted over the years near Fremont, which took place on the southern segment of the Hayward Fault, have shown that the average interval between the fault's past five significant earthquakes — tremors averaging more than six on the Richter scale — is about 50 years. The average interval of the past 11 large earthquakes, however, on this segment of the fault is much longer, around 80 years.
But the Working Group for California Earthquake Probability still predicts there's a 27% probability that the Hayward-Rodgers Creek Fault system could produce a magnitude 6.7 or larger earthquake within the next 30 years.
Because the Richter scale isn't a linear progression in regards to severity — i.e. a magnitude three earthquake isn't actually half as destructive as a magnitude six tremor — a looming quake of the aforementioned size would, theoretically, contain 1,500 times more destructive energy than today's comparatively light shaking. And best believe you (and everyone else within about a few hundred miles of its epicenter) would feel that magnitude 6-plus tectonic event.
Photo: Screenshot via USGS