Quake hits on Hayward Fault, which is due for major temblor

ByWayne Freedman, Eric Thomas, and Janet O KGO logo
Tuesday, August 18, 2015
Quake hits on Hayward Fault, which is due for major temblor
A 4.0 magnitude earthquake that rattled the Bay Area struck on the Hayward Fault, which a UC Berkeley seismologist says is statistically 10 years overdue for a 7.0 temblor.

PIEDMONT, Calif. (KGO) -- The 4.0 magnitude earthquake that rattled the Bay Area on Monday was a rude awakening for both people and pets and is yet another reminder that the Hayward Fault is long overdue for a major quake. There were several aftershocks following the temblor, which was centered in Oakland's Upper Rockridge neighborhood near Holy Names High School.

The quake was not strong enough to cause damage, but it certainly enough to bring the morning routine to a brief standstill. BART reported major delays in the morning while crews checked the tracks. No damage was reported.

Life was good and pleasantly predictable for a couple of dogs named Guss and Gizmo in Alameda until about 6:49 a.m. Their reactions, caught on camera, were typical of anyone who felt the 4.0 quake as it shuddered through the East Bay, a little past dawn.

Surveillance video from a 7-Eleven on Thornhill Drive shows customers reacting to the shaking inside the store. They stopped and looked around to see if anything fell. And though nothing did, there were still some jittery moments.

"I was helping this one customer and everything out of the random blue started shaking," said 7-Eleven clerk Alex Lesqueea. "So everyone was, like, nervous."

Truck driver Dale Stones added, "I came around the corner with my cart and I noticed all the people were coming out of the store with their hands up backing up like this and I thought first thing was, oh could be a robbery. And I backed up and then they said, 'oh it's okay it's okay, we just had an earthquake."

The epicenter was in an Oakland neighborhood near Piedmont. Imagine awakening with the earthquake happening directly below you, even if it was five miles down.

"Hey, I'm glad that if it was going to be underneath us it was a really minor earthquake," said Oakland resident Sara Osowitz.

Gentle would be a relative term.

"So it is close to a part of the fault that we do consider to be a possible source of a much larger earthquake," said UC Berkeley seismologist Roland Bergmann, Ph.D.

At the UC Berkeley Seismological Laboratory, Dr. Bergmann measured not only the main shock, but also eight aftershocks ranging between 1.4 and 2.4. All were on the Hayward Fault, which is statistically 10 years overdue for a 7.0. The next will likely to do immense damage in a densely populated Bay Area.

"I noticed that I don't have any tables at home to hide under so maybe I should buy a table," said East Bay resident Julie Miller with a laugh.

Such a quake would make the 1989 Loma Prieta seem mild by comparison. Experts tell us this is not an if, it's a when. And what we felt Monday morning was not it.

Bergmann:"We will see in a few days if this was a pre-shock."

Freedman: "You're laughing?"

Bergmann: "Yeah. That was uncomfortable laughing."

This was the second 4.0 quake people in Piedmont felt in a month. The last one was centered in Fremont. Many people we talked to say it was strong enough to get them out of bed but not strong enough to cause any damage.

"It felt like a truck hit the house," said Piedmont resident Danielle Hilton.

Fellow Piedmont resident Mary Rutherford added, "It was loud. It was the noise that really told me what it was. I felt the dog jumping into my arms and then I felt a big jolt. And the pictures were shaking on the bureau. Probably lasted few seconds.

Perhaps the only person undisturbed was 6-year-old Ruben Leunig.

"I was too busy sleeping," he said.

But many others felt it, including Ruben's mother Sheila Leunig.

"It did it got us out of bed earlier than we wanted to," she said.

Those few seconds did topple some things over. People on social media reported broken clocks and plates.

"Things fell out of medicine cabinet it was scary was wondering if more was coming but it was over fast," said Hilton.

There were several aftershocks along the Hayward Fault. The biggest was a 2.4 magnitude quake. After those, the excitement was all over and things were back to normal.

Mulberry's grocery was as busy as usual, where many get their morning caffeine. The manager was surprised that nothing fell off the shelves. They just experienced a shake of the doors.

The city says it's been working with neighbors to be earthquake prepared and Monday further drives that mission.

"Bigger quakes are few and far between we want to make sure our residents are prepared when big one does happen," said City of Piedmont spokesperson John Tulloch.

"That was definitely the discussion this morning in the bedroom -- we gotta get our stuff together," Sheila said.

Seismologists believe this fault line is the most likely location of the Bay Area's next big earthquake, but they stress that Monday's quake probably isn't a precursor.

"That's always a possibility if we look statistically over the range of earthquakes that have happened here in California," said Keith Knudsen with the USGS. "Roughly 5 to 10 percent of them are followed by bigger earthquakes over the next week or so. So it's possible this could lead to a bigger earthquake but the likelihood is relatively low."

According to Knudsen, the shaking intensity was greater than expected for a 4.0 quake because it was relatively shallow, only about three miles beneath the surface.

This earthquake comes almost exactly one year after a 6.0 magnitude earthquake hit Napa. Monday will mark the anniversary of the quake along the West Napa Fault, a buried fault line which had never been mapped. Dozens of buildings were damaged and the shaking caused over $300 million in damage. A ceremony will be held at Veterans Memorial Park in Napa to market the anniversary.

The Napa quake was the largest temblor to hit the San Francisco Bay Area since the magnitude-6.9 Loma Prieta earthquake in 1989 on the San Andreas Fault.

The California Emergency Management Agency is reminding people statewide to be ready for any type of natural disaster.

We're all encouraged to have emergency kits stocked with items including:

  • Battery operated radios
  • Flashlights with extra batteries
  • A three-day supply of food and water for everyone in the family
  • A manual can opener.
  • Click here to check out Prepare NorCal's guidelines for stocking your emergency kit and developing an emergency plan for your family.