BERKELEY — After nearly 8 million people in the San Francisco Bay Area were shaken — and some awakened — early Thursday when a magnitude 4.4 earthquake centered 8 miles below Berkeley rocked the region, authorities pointed out that the outcome could have been much more dramatic had the shaking that accompanied it been stronger.
At the same time, federal officials continue to warn Californians that there’s a 72-percent likelihood that at least one monster temblor of magnitude 6.7 or greater is destined to strike somewhere in the San Francisco Bay region before 2043. And the Hayward Fault is a prime suspect when it comes to potentially deadly fault lines.
“The thing that makes us worried about the Hayward Fault and makes it the most dangerous is that everybody is built on top of the Hayward Fault — it’s a very urban area,” said U.S. Geological Survey spokeswoman Leslie Gordon, who characterized Thursday morning’s shaker as “minor/moderate. Whereas if you look at the San Andreas Fault, it’s mostly on a lot of open space — going up the spine of the Peninsula; there’s not a heavy population right on top of the fault.”
No serious damage or injuries were reported Thursday in the aftermath of the 2:39 a.m. shaker, but the USGS said the temblor could be felt more than 150 miles away from the epicenter, which was located below the historic Claremont Hotel near the Oakland-Berkeley border. People reportedly felt the shaking for between five and 10 seconds, according to the agency.
At the hotel, an iconic architectural masterpiece originally built as a private residence during the California Gold Rush, the night staff reported feeling a good jolt as the quake emanated from eight miles below them. Hotel spokeswoman Julie Abramovic, who lives nearby, said she experienced her first earthquake since moving recently to California.
“It was scary,” she said. “It woke us up. We kind of realized what was happening, and then we were wondering, ‘What’s next?’?”
Abramovic and her family moved a year ago from Pennsylvania and though they were aware and as prepared as possible for a shake, she said there really wasn’t anything that could’ve gotten her ready for the experience of it.
She added: “This was my first big one, so I’ve got it under my belt now.’’
The quake struck in the thick of the Hayward Fault, an underground ribbon notorious for seismic risk, and it once again served as a reminder of the threat lurking from a fault that’s the Bay Area’s most overdue for a major quake. Using information from recent earthquakes, improved mapping of active faults, and a new model for estimating earthquake probabilities, the USGS in 2014 updated its 30-year earthquake forecast for California. It concluded that there is a 72 percent probability (or likelihood) of at least one earthquake of magnitude 6.7 or greater striking somewhere in the San Francisco Bay region before 2043.
“It woke me up,’’ said Albany resident Keith Knudson, who is also the deputy director of the earthquake science center at the USGS. “I have to admit I was wondering if it was a larger event.’’
He said a good rule of thumb is: How intense is the shaking and how long does it last?
In general, Knudson noted, there is a 1 to 5 percent chance that any earthquake will be followed by a bigger one.
He said USGS data indicates that the probability of an earthquake with a magnitude greater than Thursday’s 4.4 quake is 10 percent over the next several days.
“But the probability of a big earthquake, say with a magnitude 6.0 is really quite low — a 0.4 percent chance,’’ he said.
Still, he cautioned that “we live in earthquake country, so it makes sense to recognize that and take reasonable actions.’’
As in many disaster-prone areas, he said, “some people are not going to be available to help them — from police to firefighters, or hospitals — they are going to be overwhelmed. So we need to be ready to be self-sufficient.’’
Thursday’s early morning jolt “got me straight out of bed,’’ said Cupertino resident Nan Serrato, prompting the 70-year-old to turn on the lights in her home and begin taking stock of her earthquake emergency supplies. “I dug out my flashlight and made sure I had good batteries, and I double-checked the water. I have canned goods for eons.’’
She said she thought the quake might be a “pre-warning,’’ so she turned on the TV to watch the news coverage; she was surprised to find out the epicenter was not in San Jose but in the East Bay.
Already up, Serrato said she couldn’t go back to sleep. None of her grown children living in the area had contacted her, which did not surprise her because she said they were all heavy sleepers.
Daughter Jeanette Ingalls, who lives in South San Jose, slept right through the event.
“I didn’t feel a thing,’’ said the 52-year-old insurance adjustor who found out about the quake through Facebook and qualified to her friends on the social media site that “I’m a heavy sleeper.’’
Asked about her mother’s industrious reaction, Ingalls chuckled. “I”m not as prepared as my mother, that’s for sure — but we do have a five-day supply of stuff in the garage.’’
The last Bay Area earthquake that was higher than 4.4 magnitude occurred on Aug. 24, 2014, when residents of Napa were jolted awake by a strong, magnitude 6.0 earthquake — the largest in the San Francisco Bay Area since the 1989 magnitude 6.9 Loma Prieta quake.
A USGS report said the South Napa earthquake shifted houses off their foundations, damaged chimneys, started fires and broke water mains throughout the city, causing hundreds of millions of dollars in economic losses.
Thursday’s quake was originally reported as 4.7, but was later downgraded to 4.4 by the USGS. It was widely felt from Santa Rosa to Gilroy.
“One would expect a lot of people to feel this size quake in the Bay Area,” said USGS geophysicist Jack Boatwright, who awoke to a few seconds of shaking at his San Francisco home. But, he said, “the motions look about half as strong as you would expect for this size earthquake.”
Boatwright said the strongest ground motions were felt in the Emeryville area.
“Because of the size of the earthquake, we’re on alert if it will possibly be a foreshock of a bigger quake,” Boatwright said. “But there have been no aftershocks yet.”
Oakland Fire Department Lieutenant Dan Robertson tweeted: “Nothing like being upstairs in a 106-year-old firehouse made of poured concrete, despite having been “Retrofitted” in the early 90’s … The brass fire poles were rattling!”
There were no immediate reports of damage, according to the California Department of Emergency Services. Although BART initially said in a statement that commuters should expect “major delays with our first trains this morning,” the system’s tracks were quickly inspected and all trains were back running on schedule by about 4:45 a.m., the agency said on its Twitter account. BART said that “in an abundance of caution” they were running the first trains at reduced speed “for another visual inspection by the operator.”
Along Domingo Avenue, directly across from the historic Claremont Hotel up the hill, workers opening the Peet’s Coffee shop and Rick and Ann’s restaurant around 7 a.m. said that there was no damage to their businesses.
Fred Tealdi, a longtime employee at Montclair Village Hardware off Highway 13 and not far from the epicenter, said several customers on Thursday had mentioned being awoken by the quake, but nobody was stocking up on things like devices to strap bookshelves to walls.
“We all live on the fault up here,’’ he said. “And while a couple of people mentioned the rattling that woke them up, nobody was really panicked, knowing it was only a 4.5.’’
Come with the territory, said Tealdi.
“Most of our customers know what to expect living around here,’’ he said of the middle-of-the-night shaking. “We all get used to it.’’
For Northern Californians, the Hayward Fault is the most likely source of a dangerous quake, with a 33 percent chance in the next 30 years.
The Hayward Fault, part of the larger San Andreas Fault system, runs from San Pablo Bay in the north to Fremont in the south — passing through the heart of Berkeley, Oakland, Hayward, Fremont and other East Bay cities.
The USGS said the last large quake on the Hayward Fault was in 1868, with an estimated 6.8 magnitude. It killed about 30 people and caused major property damage.
But the population of the East Bay is now about 100 times larger — so many more people will be affected by the next major quake.
The region is a place of ongoing and often imperceptible earthen creeping, as evidenced by routinely broken sidewalks in Hayward and Fremont. If you stand in the Bay Area and look toward the Sierra, over time you’d see the mountains move to the right.
The Hayward Fault creeps about one-fifth of an inch a year.
Local utilities reported no structural damage from Thursday’s quake. CalTrans spokesman Bob Haus said 4.4 magnitude quakes “usually doesn’t do too much damage’’ to roads or bridges; anything under 5.5. magnitude or less. “But you always build in flexibility on things like that,’’ he said, adding that CalTrans crews will go out and do inspections if there is other reported damage in the area. So far, that did not appear to be the case.
And Jenesse Miller, a spokesperson for EBMUD, said the quake had no “impact on EBMUD operations or facilities. Per EBMUD’s standard response protocols after an earthquake, staff conducted inspections of the water treatment plants, wastewater treatment plant, and other critical facilities. Though the epicenter was near several EBMUD reservoirs and pumping plants, there were no operational impacts or damage to our facilities.
Miller identified the reservoirs in question as: San Pablo, Lafayette, Briones, Upper San Leandro and Chabot.
Staff writers Rick Hurd, Kathleen Kirkwood and Matthias Gafni also contributed to this story.
Article source: https://www.mercurynews.com/2018/01/04/4-5-quake-jolts-east-bay/