Stronger Earthquakes Predicted for San Francisco Bay Area

It has been about 8 weeks since the 6.0 South Napa Quake struck at 3:21am.


The town is still recovering, red tags are being removed from homes and people are moving back in. Most establishments have reopened and back to buisness as usual, while a few are still closed or relocated in to trailers.

6-8 weeks is about the timeframe my doctor gave for my earthquake related anxiety (traumatic stress) to stop. It's been about 8 weeks and I'm no longer fixated on the quake, checking all sorts of apps for earthquakes, all in all I'm starting to feel normal again!

Right on time for the news that 4 California Faults could produce up to a 6.8-7.1 magnitude quake! Perfect timing

The South Napa Earthquake was centered in between two other major faults, the Rodgers Creek Fault and the Green Valley Fault that run through the hills on either side of the valley:


Creep in 4 Faults Means Big Quake may be Poised to Hit

Four highly stressed seismic faults in the Bay Area’s densely populated San Andreas system are moving on the surface and could rupture in a major earthquake at any time, according to scientists tracking their movements.

Those 4 faults are:
• The Green Valley Fault
• The Rodgers Creek Fault
• The Hayward Fault
• The Calaveras Fault

Lienkaemper and his colleagues have been analyzing the rates of those tiny continuous movements along Northern California faults for years. The movement is only a few millimeters a year, but the effects over the years can be visible in roadside cracks and offset curbs.

A part of The Green Valley Fault that runs along a roadside by Rockville Park:


Last major Earthquake on the four faults:
• The Green Valley Fault: about 1609
• The Rodgers Creek Fault:last major quake in 1745 according to evidence uncovered by scientists
• The Hayward Fault: estimated 6.8 in 1868
• The Calaveras Fault: about 1740

“Given how long ago they had their last earthquakes, they are more than ready to produce a major earthquake again now,” said Roland Burgmann, a geophysicist and expert on crustal deformation at UC Berkeley who was not involved in Lienkaemper’s report.

• The Green Valley Fault: could produce a magnitude 7.1 earthquake
• The Rodgers Creek Fault: could produce a magnitude 7.1 earthquake
• The Hayward Fault: is considered the most likely to rupture, it could trigger a magnitude 6.8
• The Calaveras Fault: could produce a magnitude 6.8 earthquake

Stronger Earthquakes Predicted for Bay Area—and They Could Come Soon: A new study improves tremor forecasting of major northern California faults
When Will The Big One Hit?

In the case of the Hayward Fault—which runs through Oakland, Berkeley, and other heavily populated East Bay locales—the team was able to look at the geologic record going back about 2,000 years and found that major earthquakes have tended to hit there about every 150 years. The last big one was in 1868, 146 years ago, so another one is expected at any time.

The Rodgers Creek Fault, which runs northwest from the bay through the wine country of Sonoma County, is about 90 percent "locked," meaning the rocks are stuck and the strain is building. "A large earthquake is likely there," says Lienkaemper, though he notes that because there hasn't been an earthquake on the fault in historical times or evidence of one available in the geologic record, the timing is hard to predict.

Similarly, because the Green Valley Fault is a complex, crooked system with an uneven seismic history, predicting exactly when the next big one will hit there is also difficult.

So it's practically impossible to determine exactly when an earthquake will strike, the USGS, SCEC and the California Geological Survey give us a 99.7% chance of a Big One hitting somewhere California in the next 30 years. The question is, will The Big One be on one of the four at risk faults?
Big Quake "Guaranteed" to Hit California by 2037
A December 2007 report (compiled by the combined effort of the USGS, Southern California Earthquake Center (SCEC), and California Geological Survey) gives a 99.7% chance of a magnitude 6.7+ will strike somewhere in California in the next 30 years, 2037. The Green Valley Fault and Rodgers Creek Fault aren't listed as being in the top 7 but the report is from 2007.

The first statewide earthquake forecast for California calculated the probabilities that a magnitude 6.7 or larger temblor will occur along seven of the state's major faults. At 59 percent, the southern part of the San Andreas has the highest chance of rupturing and creating a major quake.

While I feel anxiety creeping back again, it's good to be aware of the risks of an earthquake occurring.

Being saddled in between two of the faults listed as at risk, The Green Valley and Rodgers Creek Faults, is a little more than nerve wracking. However, it's a good reminder to stay prepared, have an emergency food, water, first aid etc supply, evacuation plan and meeting places.

It's easy for Californians to forget we live in Earthquake Country since they don't happen all the time.

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Some of my pictures from the day of the South Napa Quake (8/24/2014)



My friends apartment entrance:

A couple satellite images of the damage from the Napa Quake (more at the link)


The Napa Earthquake in Satellite Imagery
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Further reading:
Interesting article about coping after traumatic stress using Loma Prieta and the (first) Gulf War as examples

Geological Outings Around the Bay: The Cordelia and Green Valley Faults

Powerful Earthquake Faults Threaten Napa on 2 Sides

The next 'Big One' for the Bay Area may be a cluster of major quakes

When will the Big One strike California?

Scientists also warn of cluster quakes and are looking in to the areas past history of earthquakes to gain a better understanding of what may happen decades in to the future:

The study, which is expected to come out in the June 2014 issue of the journal [pdf] Bulletin of the Seismological Society of America, observed a natural cycle of earthquakes between 1690 and 1776, the year when the city of Mission Dolores and Presidio of San Francisco were both founded.

In the span of almost a hundred years, California experienced a cluster of tremors ranging from magnitudes of 6.6 to 7.8.

Prepare for cluster of strong earthquakes in Bay Area, experts warn

This article was from May 2014, a few months before the August 24th quake. I wonder if the South Napa Quake is the first of a cluster or if it will be a stand alone event. Time wil tell...

The study mentioned above:
The Earthquake Cycle in the San Francisco Bay Region: A.D. 1600–2012

The Great 1906 San Francisco Earthquake

a reply to: Jennyfrenzy

The Hayward fault has been worrying me for years, I've seen the creep first hand.

We are long overdue.

a reply to: Mrs.Peony

The Hayward Fault is a scary one, it runs right through the East Bay and would do some major damage if it were to burst.



Were you around for the Loma Prieta Quake? Can't believe it's been 25 years! I didn't feel that one, my family was in the car when it hit. When we got home there was no power, the house was disheveled and there were puddles of water around the swimming pool.

a reply to: Jennyfrenzy

I was working in Palo Alto at the time....however, I was on vacation in Idaho, so missed all the excitement. Our company building had LOTS of damage, as did my apartment in Cupertino.

I had always said I would prefer to be up in Idaho at my aunt's ranch when Armageddon hit. So I find it somewhat ironic.

When I worked in the Bay Area I always kept sleeping bag, tent, stove, 72-hour kit in my trunk. I now live along the Wasatch Fault...just as apt to break loose any day...but I'm not quite as prepared...

a reply to: Jansy

You missed it too!

I was working in Palo Alto at the time....however, I was on vacation in Idaho, so missed all the excitement. Our company building had LOTS of damage, as did my apartment in Cupertino.

It's funny how things work out like that sometime!

It's always good to be prepared. I realized just how unprepared I was after the Napa Quake, we didn't have power for
almost two days. Now there's two backpacks, packed and ready to go along with a storage container filled with food, first aid, a carton of cigarettes, batteries etc.