Residents of the bay area of California were shaken awake today as a result of a strong 4.5-magnitude earthquake. The earthquake was centered below Berkeley, California and was a result of movement along the Hayward fault, according to the USGS.
The earthquake began at 2:39 a.m. local time, located directly over the Claremont Hotel in Berkeley, which woke many residents of Berkeley and nearby cities. Residents across the San Francisco Bay area, as far south as San Jose, and as far north as Santa Rosa said they felt shaking. At this time, there are no significant reports of personal injury or structural damage and no threat of a tsunami.
The USGS classified the earthquake as moderate, occurring 8 miles into the earth, but warn there could well be small aftershocks in the coming days. They estimate that the probability of another strong earthquake striking the bay area is between 5% and 10%.
USGS
Locals say they felt shaking for 5 to 10 seconds and became worried about structural damage to their homes. However, magnitude 4.5 earthquakes often don't result in significant structural damage but are certainly powerful enough for people to take notice.
The earthquake was a result of movement on the Hayward fault, which runs right through Berkeley to the east of San Francisco. The fault runs roughly parallel to the San Andreas Fault, which lies to the west of the Berkeley fault. The Hayward fault, as it runs south, eventually merges into the Calaveras fault. This suggests any movement on the Hayward fault could translate to movement on the Calaveras fault to the south.
Felt a big jolt and rolling. Picture frames, etc, fell down. We are standing outside because the fire alarm went off. SFPD & SFFD is here now. #earthquake pic.twitter.com/8dMu58spUt — Riya (@loislane28) January 4, 2018
The origin of the Hayward fault is the constant northwestward sliding of the Pacific Plate at 5 millimeters per year against the North American Plate, producing a transform boundary. This transform boundary results in the San Andreas fault along with the Hayward fault. This constant movement between the two tectonic plates is experienced through sticks and slips between two fault planes. As strain builds up against the system of strike-slip faults, eventually the rock fails and there is fault displacement, i.e. an earthquake. Historically, the Hayward fault produces a large earthquake every 160 years, however, the margin of error (80 years) and little historical data makes predicting earthquake frequency difficult.
USGS
While it may not seem like a net positive, the fact that the Hayward fault slipped and produced a magnitude 4.5 earthquake is not entirely bad. The reasoning is that eventually, these faults (Hayward, San Andreas, etc.) will move. A worse case scenario is that enough strain is built up over time due to the lack of slip along the fault that it triggers a massive earthquake at magnitudes 9 and above.
The fact that the Hayward fault produced a magnitude 4.5 earthquake means it has, albeit temporarily, reduced strain on that part of the fault without further building up. Given a magnitude 4.5 earthquake is large enough to be felt but not large enough to cause significant structural damage or injury is in an ideal zone with regards to releasing strain on the system.
The potential for the Hayward fault to produce a 7.0 magnitude earthquake is there. In addition, the fault lies directly below approximately 2 million people, substantial infrastructure, as well as water, gas, and electric lines. While some other faults may have the potential for more substantial earthquakes, the location of the Hayward fault makes it one of the most dangerous in the United States.
While we can be assured that California will continue to experience earthquakes like the one today, we can hope they are regular and at small enough magnitudes as to not cause significant destruction.
San Francisco (CNN) A 4.4 magnitude earthquake struck early Thursday in Berkeley, California, according to a preliminary report from the US Geological Survey, jolting some residents of the densely populated San Francisco Bay area awake in their beds.
The earthquake hit at 2:39 a.m. local time (5:39 a.m. ET), centered near the Berkeley-Oakland boundary.
There were no immediate reports of damage in the area, the state Governor's Office of Emergency Services said.
No reports of damages from the region at this time. #earthquake #whatsshakincalifornia https://t.co/cSPgzjoMb5 — Cal OES (@Cal_OES) January 4, 2018
Some residents in the area told CNN affiliate KPIX that the quake shook them awake. A quake of this intensity generally would produce moderate shaking felt by nearly everyone near the epicenter, awakening many people and having the potential to break some windows and dishes, the USGS says
"It shook our house and shook the bed big time," Gina Solis of San Rafael, across the San Francisco Bay from Berkeley, told KPIX
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SAN FRANCISCO— It was a sharp jolt, but also a warning of something much more violent that could be coming.
An estimated 9.8 million people felt a magnitude 4.4 earthquake that rumbled across the Bay Area early Thursday, the U.S. Geological Survey reported.
It was felt throughout the region, with people more than 150 miles away reporting to the agency that they felt the shaking for perhaps five to 10 seconds.
The epicenter of the earthquake is in the area of the Hayward fault, one of the most feared in the Bay Area, which could produce a magnitude 7 or greater earthquake and is directly underneath heavily populated areas.
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.
Thursday’s quake was tiny by comparison and did little damage to speak of.
The shaking was strong enough to wake people up when the earthquake hit at 2:39 a.m. One person in San Francisco said it was strong enough to knock picture frames from the wall.
As is always the case, there was a 5% chance the temblor could trigger a larger quake in the near future.
“We live in earthquake country so we should all expect earthquakes,” said Keith Knudsen, deputy director of the USGS Earthquake Science Center. “There will likely be aftershocks. There’s a small probability there will be bigger ones.”
An earthquake early warning system under development worked — and sent data about the temblor to computers 4 seconds after it began, Knudsen said.
In a real-world scenario, the jolt felt Thursday would likely not be considered big enough to issue a warning to residents in the path of the shaking, he said.
“But having one up and running and testing it is really valuable to us. How much warning time one gets depends on how far away they are, how big it is, how dense the seismic network is and how rapidly the computers are processing,” he said.
The system would typically allow a few seconds of warning for people not close to the epicenter — which would be enough time in theory to slow trains, stop elevators and allow people to brace themselves.
When asked Thursday at a news conference whether Californians were ready for an earthquake, Knudsen demurred.
“I’d ask you are you prepared?” he said. “We’re doing better than we used to do. But there’s more that can be done.”
The earthquake was felt as far away as Marin and Sonoma counties, and the Silicon Valley. Some Bay Area residents reported that the earthquake woke them up.
“Only M4.5, the size we have several times a year in California,” tweeted seismologist Lucy Jones. “But when you are right on top of a quake, it feels much stronger.”
The Hayward fault courses right 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’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.
USGS Geologist David Schwartz says Thursday morning quake occurred on seismically active 'hot spot' on Hayward Fault USGS Geologist David Schwartz says Thursday morning quake occurred on seismically active 'hot spot' on Hayward Fault SEE MORE VIDEOS
The Hayward fault is considered one of the nation’s most dangerous faults because it is located 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 USGS 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 U.S. Geological Survey geologist, said in an interview that above the Hayward fault are “two 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.”
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Lin reported from San Francisco, Serna from Los Angeles.
ron.lin@latimes.com
@ronlin
UPDATES:
4 p.m.: This article was reworked at the top with new lede.
7:50 a.m.: Updated with downgraded magnitude to 4.4 and comments from USGS officials.
6:40 a.m.: Updated with no reports of damage or injuries in San Francisco.
3:35 a.m.: Updated with context about the Hayward fault.
3:10 a.m.: Updated with locations where the earthquake was felt.
3:02 a.m.: Updated with quote from a USGS seismologist.
This article was originally published at 2:55 a.m.
San Francisco Bay Area residents have been shaken out of their slumber by a magnitude 4.4 earthquake that was felt over a wide area.
The quake struck at 2.39am about 2 miles (3km) from Berkeley, just across the bay from San Francisco, according to the US Geological Survey.
The magnitude was revised after it was initially reported as magnitude 4.5. It happened at a depth of 8 miles (13km).
The quake struck about 2 miles ( 3km ) from Berkeley, just across the bay from San Francisco ( USGS )
Social media posts showed people were woken up some 40 miles (64km) to the north and south.
A spokesman for the California Governor's Office of Emergency Services said there were no reports of harm to the region.
A Berkeley Fire Department dispatcher, who declined to give his name, said more than a dozen people had called, mostly complaining about windows shaking. He also said there were no reports of any damage or injuries.
“Felt like a big truck drove into the building or something blew up downstairs. It just rocked the room and bed like two or three times quickly with a decently loud rumble in North Berkeley,” Dale Fest wrote on the San Francisco Chronicle's Facebook page .
Bay Area Rapid Transit said it had checked tracks for damage and found no problems. Early delays in train service were cleared up by 5.30am, the agency said.
Jack Boatwright, a geophysicist with the USGS Earthquake Science Center in Menlo Park, said the shaking from the quake “seemed a little weak, about half as strong as what you would expect.”
He told the Chronicle that by 4.15am, there had been no aftershocks, which he called “a good sign. It may mean less likelihood of a larger earthquake to follow.”
Twitter lit up with comments, many of them light-hearted.
Since everyone in the Bay Area is awake, it's time for the 30 minute dance party! #earthquake pic.twitter.com/Z4L0sSgsK0 — Troop 206 Oakland Ca (@Troop206Oakland) January 4, 2018
*wakes up to earthquake in san francisco*
*freaks out*
*checks twitter*
*goes back to bed* — Taryn Arnold (@Thetarynarnold) January 4, 2018
"Since everyone in the Bay Area is awake, it's time for the 30 minute dance party! #earthquake," one user wrote.
Another described how the earthquake woke them up: "*wakes up to earthquake in san francisco*, *freaks out*, *checks twitter*, *goes back to bed*"
San Francisco earthquake got me like pic.twitter.com/vOLkQfQKbb — SpiritedLA (@spiritedla) January 4, 2018
Around an hour after the quake, San Francisco's Department of Emergency Management sent a text to residents saying there was no tsunami warning.
Additional reporting by agencies
