Santa Rosa earthquake: This little-known fault could soon produce the Big One

[Auggie]

San Francisco Chronicle / September 14, 2022

A magnitude 4.4 earthquake hit Santa Rosa at 6:39 p.m. Tuesday, followed by a magnitude 4.3 aftershock one minute later. They knocked picture frames off walls, cracked water pipes and rattled nerves.

The U.S. Geological Survey pinned the epicenter on a portion of the Rodgers Creek Fault that runs under the Hidden Valley neighborhood near Fountaingrove in northeastern Santa Rosa.

SNIP

The Rodgers Creek Fault is the northern spur of a fault that ends in the hills north of Healdsburg and extends southeastward through central Santa Rosa and under the San Pablo Bay, where it becomes the better-known Hayward Fault that runs under the urban East Bay and had a major rupture in 1868.

Scientists estimate that these connected faults have a 33% probability of experiencing a major earthquake of magnitude 6.7 or higher before 2043. Made by a group of scientists with the USGS, the Southern California Earthquake Center and the California Geological Survey, this forecast put these faults as the most likely sources of the Bay Area’s next devastating earthquake.

Link (paywall): https://www.sfchronicle.com/bayarea/article/Santa-Rosa-earthquake-Little-known-Rodgers-Creek-17441486.php

Additional highlights (from the link):

• USGS scientists found evidence showing the Rodgers Creek Fault ruptured significantly in the early to middle 18th century.

• Scientists are studying whether the recently discovered connection between the Rodgers Creek and Hayward faults under the San Pablo Bay might indicate they could rupture together, generating a large-scale disaster.

• Any earthquake brings a 5% chance it will be followed by a larger one within about three days.

• Magnitude 4 earthquakes are relatively common and unlikely to have released much tension along the fault.

That last bullet point is news to me. I've been led to believe they did.

[relayerbob]

1. 6.7 isn't "the big one"

It’s big enough, but I’ve been in bigger. They can get far larger.

[Auggie]

3. 6.7 or larger, according to the link. 6.9 would equal Loma Prieta.

[relayerbob]

5. Yes, was there, not far from San Andreas

Rocked enough for my taste, but I would consider "the big one" to be at least mid 7s, at least, and often 8s are used in that context. 50-100x as powerful, or more.

[BittyJenkins]

2. We felt it...

Our little terroir felt it before we did. She was running around barking.

[alwaysinasnit]

4. My daughter and I were having dinner when we felt the first one. She immediately grabbed my

arm and pulled me away from the hanging glass light fixture overhead. It had started swaying a bit, and swung more with the aftershock. It kept us unsettled for the rest of the evening. (I'm 10 minutes south of Santa Rosa.)