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 percent.
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.
- A 4.4 magnitude earthquake shook the Bay Area early Thursday morning.
The quake struck at 2:39 a.m. and was centered two miles east/southeast of Berkeley on the Hayward fault according to the USGS.
According to Keith Knudsen with the USGS in Menlo Park, there hasn't been a major earthquake on the Hayward fault in over 100 years. A magnitude 6.8 tremblor struck the Hayward fault on October 21, 1868 killing 30 people and causing widespread damage. "It's a great reminder the Hayward fault is ready to go," Knudsen said.
Knudsen said there was one aftershock recordered following Thursday morning's quake and said there is a small probability it will be followed by a bigger earthquake. Historically, he said about 5% of earthquakes are followed by larger ones.
Randy Baldwin, a geophysicist with the USGS said the quake was eight miles deep which is fairly shallow. He said the quake was widely felt about 100 miles beyond the epicenter and that a magnitude 4.4 earthquake is a common size for the area.
The quick jolt woke many people up. The KTVU newsroom was flooded with callers who felt the shaking all the way north to Cotati and South to Gilroy. A few people reported items had fallen off shelves.
BART said riders should expect delays while the inspect their system as is routine after an earthquake. Officials said there were no initial reports of damage and trains were back on schedule at around 5:45 a.m.
Expect major delays with our first trains this morning. Trains will be performing track inspections due to earlier seismic activity. — SFBARTalert (@SFBARTalert) January 4, 2018
VTA said it is conducting routine checks of its tracks as part of its standard safety precautions. Riders should anticipate minor delays.
Alert SF said there is no threat of a Tsunami and the California Office of Emergency Services said there were no reports of damage.
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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A magnitude 4.5 earthquake shook up the San Francisco Bay Area early Thursday.
It was felt throughout the region, and could be felt for perhaps five to 10 seconds. Near the San Francisco International Airport, several jolts could be felt.
Items in a San Leandro store were knocked off the shelves, video from KRON4 showed, and Bay Area Rapid Transit started Thursday with train delays as workers performed a system-wide check for damage about 4 a.m.
The checks were completed about 5:30 a.m. with no reports of damage, the agency tweeted.
The earthquake was centered along the Oakland-Berkeley border, just north of the Claremont Hotel. 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.
San Francisco’s emergency managers said all city facilities and infrastructure would be inspected Thursday, though there were no initial reports of damage or injuries.
A magnitude 4.5 earthquake is not expected to cause major damage, said U.S. Geological Survey seismologist Robert Sanders. Still, “there’s always a possibility of some minor damage to older structures in the area.”
The shaking was strong enough to wake people up when the earthquake hit at 2:37 a.m. One person in San Francisco said it was strong enough to knock picture frames from the wall.
The earthquake was felt as far away as San Francisco, Marin County, Sonoma County and 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.
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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ron.lin@latimes.com
@ronlin
UPDATES:
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.
