M4.6 Earthquake – 2 km ESE of Berkeley, CA (opens in new tab)

It was centered half a mile from Berkeley Lab at 2:56am, on the Hayward Fault. Knocked out the elevators in my building and one other building, but other than that no obvious issues. We've been told to be on alert for anything that looks off. Hard to predict how this affects some of the Lab equipment.

FWIW, I've been expecting something like this. The Pacific Rim ("ring of fire" or whatever you want to call it) has been overly active, and that second 7+ magnitude earthquake in Kamchatka was definitely not a coincidence. That said, earthquakes are not my area, but it is a topic we talk about in terms of catastrophic failure of storage systems as "Hayward Fault Tolerance" where we have tertiary backups in a region outside of the earthquake zone.

Mid-4s is where most people start feeling quakes, though the actual significance is pretty low. You'll tend to see/hear a lot of chatter online or in media.

At mag 5 there's localised damage, most characteristically of goods knocked off grocery store shelves, with glass-bottled liquids often producing a photogenic mess.

At mag 6, pre-code construction or at-risk areas (bay fill, river bottoms, sand) may see significant structural damage. The 2014 South Napa earthquake is the most recent of these, and downtown Napa was hit pretty hard, due to terrain (reclaimed river bottomlands, bay-fill, and some old masonry construction). See: <https://en.wikipedia.org/wiki/2014_South_Napa_earthquake>.

Mag 7 is the scale of some of the largest quakes recorded in California, including the 1906 San Francisco quake. This would create widespread damage within 100+ miles of the epicentre. Marc Reisner's A Dangerous Place (2003) includes a detailed description of impacts of a mag 7 quake along the Hayward fault, which would extend well beyond the immediate region into Southern California due to reliance on delta and Central Valley water projects.

<https://baynature.org/article/book-review-a-dangerous-place/>

Mag 8 is about the upper bound of expected seismic activity on the San Andreas and related fault systems.

And that was just the automated response... it was downgraded to 4.3 an hour after the event.

4.3 will certainly get your attention if you're relatively close-by... but yeah, worth a "did you feel that?!" on the local news and not much more.

From someone that grew up in New England, but experienced a 4.x in california: I assure you it does not feel small.

The revelation that the ground does not stay where I left it was quite disturbing.

Many years ago a 4.5 hit when I living in Berkeley, about 2 miles aways and I thought a truck ran into my house. No rolling - just one giant jolt.

I was awake and it was definitely stonger than any I've experienced in my 3 years in SF

I'm pretty sure this is the closest epicenter to SF I've seen too (at least one that was noticeable)

Magnitude scales and felt shocks don't really correlate well. These are like Wh and V, only roughly indicative of each others. You have to look into maximum recorded accelerations.

Everyone is secretly (or openly) waiting for Teh Big One we’ve been promised for decades, when Western California will fall into the ocean and Las Vegas become a seaport.

Many of us on this website live in the bay area. The earthquake woke us up with a stern jolt and now you're witnessing a shared moment in the community as we try to drift back to sleep.

I live in a nearby city and it woke me up (bed was shaking). Felt bigger than that, but not enough to knock anything over, seems odd to be on HN front page.

Apparently 7.6km depth is "very shallow"

4.6 is small, but anything above 4 is reasonable to report.

I would assume someone new to CA would find it concerning.

It's fun to think about it - some Japanese people would move to CA just because of the more stable geology.

It is a minor earthquake, especially for a region with generally high standards and tolerances for actual earthquakes. It's enough to certainly notice (if you're awake) and make people look at each other like "Whoa, neat" but that should be the start and end of it.

The votes seem to suggest it

It’s the strongest shake the area has felt in a decade. I think it’s just the community having a bit of fun.

It's notable for people in California where a lot of HN users are based.

It's gone sooner if you don't interact with the thread...

I've lived in California all my life and was in San Mateo during Loma Prieta. How close you are to the epicenter has a strong effect on what you experience (it's undoubtedly more complicated than that but distance is a big factor). Last night's was 14.8 miles away from me and although I woke up, I didn't hear earthquaky sounds and shaking was moderate. Thought my partner had just flopped over in bed harder than usual. By contrast, a few years ago we had a 3.1 centered about 1.5 miles away that really made me fear it was a big one. The house jumped and stuff swayed, and I was just thinking I'd better get next to the bookcase when it stopped.

Same. Been 12 years in SF and this was the strongest. We were awake as well so we felt the whole thing. I think I saw the walls move.

Luckily it was short.

Second strongest I remember in my 16 years here, with the 2014 Napa Quake being notably more shaking.

I usually don’t wake up to these but this one jolted me awake. I wish I had slept through this one though.

I was 3 miles from the epicenter. By far the strongest I’ve felt since I moved here 15 years ago. Hard to imagine what a 6+ would be like on the Hayward fault.