Update | An earthquake struck the Bay Area early Thursday morning along a fault line that U.S. Geological Survey scientists have called a “tectonic time bomb.” The earthquake hit near Berkeley, California, as a magnitude 4.4. The damage is expected to be minimal, but it occurred along the Hayward fault—one of the seven fault zones in the Bay Area, according to the USGS.
The earthquake shook for about five to 10 seconds, reported the Los Angeles Times, and an estimated 9.8 million people felt the quake. The depth was about 8 miles, which is relatively shallow. Some earthquakes can be more than 350 miles deep in countries such as Fiji, according to USGS duty seismologist Robert Sanders.
“These shallower events are generally the more common events,” Sanders told Newsweek. A shallow event has a high probability to cause damage, though a much deeper event could be felt over more widespread area, he explained. “The closer to the surface, the more intense the movement and ground-shaking will be locally.” The event was felt as far east as Sacramento and beyond San Jose, to the south of Berkeley. The shaking was weak to light in most areas, according to the USGS as of Thursday morning.
Keep up with this story and more by subscribing now
The Hayward fault where the quake shook lies beneath a highly populated area in the Bay—and the next "big one" could be a magnitude 6.8 to 7 earthquake. This fault zone runs from San Pablo Bay in the north to Fremont in the south—passing through Berkeley, Oakland, Hayward and Fremont.
"We know that it's ready [and] is capable of having another big earthquake at anytime," Tom Brocher, seismologist at the USGS, told Newsweek. The Hayward fault is highly urbanized, with communities built on top of the fault, up and down the length of the East Bay. Though a 1972 law was passed that restricted new buildings from being constructed on top of the earthquake fault, older neighborhoods are still at risk. Moving further south along the Hayward fault, Brocher said, you can see the impact of the law as buildings aren't built directly on it.
"You can't get far from the Hayward fault because of the bay, so the entire East Bay is pretty close to the Hayward fault," Brocher said. "This earthquake was right in the center of the Bay Area, and it was very widely felt throughout."
The fault is considered to be “creeping” because there is evidence of it steadily slipping 5 millimeters each year. Roads, curbs and buildings are frequently offset from the “creeping.” A 2003 report determined that the Hayward–Rodgers Creek fault system would produce at least a magnitude 6.7 earthquake in the next 30 years.
The other fault zones in the region—Calaveras, Concord–Green Valley, Greenville, Rodgers Creek, San Gregorio and perhaps the most notorious San Andreas fault—all crisscross through the Bay Area region. Hayward crosses right through the football stadium of the University of California, Berkeley.
Getty
The last major quake along the Hayward fault happened in October of 1868, when a magnitude 6.8 hit the San Francisco Bay region, making it the most destructive earthquake in the state’s history. The past five large earthquakes on Hayward fault have been about 140 years apart, so this fault and the Rodgers Creek faults are the most likely to have a major earthquake in the bay.
The 1868 quake was the 12th most lethal in California history, killing 30 people. Per USGS, it was known as the “great San Francisco earthquake” until the magnitude 7.9 quake struck the San Andreas Fault in 1906.
In mid-November, an earthquake swarm struck the San Andreas fault after a 4.6 magnitude quake hit Monterey County, California. Last week, two earthquakes hit outside of San Jose. Though scientists can estimate how strong a quake could be on various fault lines, earthquake prediction is still in the future.
This article has been updated to include additional information about how widespread the earthquake was felt in addition to the dangers of a major earthquake at the Hayward fault.
SaveSave
The earthquake that rattled the Bay Area on Thursday is another reminder of the power and danger of the Hayward Fault, which runs below the populous East Bay.
The Hayward fault, along with the San Andreas fault on the San Francisco peninsula, have long posed a twin seismic peril to the region. The San Andreas produced the devastating 1989 Loma Prieta quake and 1906 San Francisco quake.
The Hayward fault could produce a magnitude 7 or greater earthquake and is directly underneath heavily populated areas.
Damage from 1868 Hayward Fault quake USGS
A sleeping giant
The Hayward fault courses underneath Berkeley, Oakland, Hayward and Fremont and produces a large earthquake, on average, every 160 years, with a margin of error of about 80 years. It has been 150 years since the Hayward fault last ruptured, unleashing a huge earthquake.
The Hayward fault is considered one of the nation’s most dangerous faults because it is directly under the urban centers of the East Bay, including Memorial Stadium at UC Berkeley and a now-shuttered building that formerly housed Hayward City Hall, which is slowly being torn up by fault movement.
A U.S. Geological Survey scenario for a 7.0 earthquake on the Hayward fault envisions it rupturing for 52 miles from San Pablo Bay to Fremont. It would cause one side of the fault to move four feet from the other. Many buildings, including apartments, still sit directly on top of the fault line, and were built before a state law passed in 1972 prohibiting new construction or substantial renovation on top of earthquake faults.
On its website, the USGS calls the Hayward fault the region’s “tectonic time bomb,” which could “cause hundreds of deaths, leave thousands homeless and devastate the region’s economy.”
In 2016, David Schwartz, a USGS geologist, said in an interview that above the Hayward fault are “2 million people who directly live on top of it. It sits geographically in the center of the Bay Area. There’s a tremendous amount of infrastructure built up on it — water systems, gas, electrical, BART crosses it — so a large event on that fault is like hitting the bull’s eye on a target.”
Here is a simulation of the power of a 7.0 quake on the fault. And a shake map.
This curb was once flush but became offset because the Hayward fault is pulling the curb apart. Rong-Gong Lin II / Los Angeles Times
A rupture in 1868
The Hayward fault’s most memorable earthquake in recorded history was in 1868, and is estimated to have been a magnitude 6.8 earthquake — rupturing 20 miles of the fault’s length between San Leandro to what is now the Warm Springs neighborhood of Fremont, according to the USGS.
It killed about 30 people and caused immense property damage, including the collapse of the Alameda County Courthouse’s second floor and heavy damage at the historic Mission San Jose adobe church in southern Fremont.
Many faults cut across California’s coastal region. What might an earthquake look like along the Hayward Fault? This simulation depicts one scenario. For more on earthquakes—why ...
‘The fault will have its revenge’
Until recently, one of the places to see the power of the Hayward fault was at the corner of Rose and Prospect streets in Hayward.
Pulled apart so that it no longer aligned, the humble curb wasn’t much to look at. But for earthquake scientists, it was a kind of Holy Grail, perfectly illustrating the seismic forces at work underneath this Bay Area neighborhood.
Since at least the 1970s, scientists have painstakingly photographed the curb as the Hayward fault pushed it farther and farther out of alignment. It was a sharp reminder that someday, a magnitude 7 earthquake would strike directly beneath one of the most heavily populated areas in Northern California.
Then, in 2016, a city crew decided to fix the faulty curb, destroying the marker of seismic power.
“They really took it out. Wow,” Schwartz told The Times. “It really was an iconic location on the Hayward fault.”
But he added a warning: “The fault will have its revenge.”
We feel so bad about the rest of the country's shitty winter, we conjured up a sympathy earthquake.
— Jeff McWhy are there nazis on this site? (@McClure_SF) January 4, 2018
