Daly City is basically the "front porch" of the San Andreas Fault. If you’ve ever walked along the cliffs at Mussel Rock Park, you’ve literally stood on the seam where the Pacific Plate and the North American Plate are trying to grind past each other. It’s a weird, beautiful, and slightly unnerving place to call home.
Most people think of 1906 or 1989 when they talk about Bay Area tremors. But for Daly City, the story is more personal.
The 1957 Daly City Earthquake: The Big One That Wasn't
Honestly, the 1957 quake is often ignored in history books, but it was a massive deal for the Westlake district. On March 22, 1957, a $5.7$ magnitude quake hit right off the coast. It wasn't the "Big One," but it was the strongest shaking the Peninsula had felt since 1906.
It happened at 11:44 a.m. One person died—a tragic accident involving falling debris—and about 40 people were injured. What’s wild is that it was an "oblique-slip" movement. Basically, the ground didn't just slide sideways; one side actually pushed upward.
Damage was concentrated in Westlake. Think cracked plaster, shattered windows at the brand-new San Francisco State College library, and a section of Highway 1 literally sliding into the ocean. Over 1,000 people had to leave their homes because of a reservoir rupture. It was a mess.
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Why Daly City is Geologically Weird
You’d expect the San Andreas to just be a straight line. It isn't. Near Daly City, the fault has these little "kinks" or curves.
- In the Santa Cruz Mountains: The fault curves left, causing compression (pushing up the mountains).
- In Daly City: The fault curves slightly right. This creates "extensional" forces. Instead of pushing up, the crust is being stretched and thinned.
This is exactly why the fault line eventually drops below sea level as it heads toward the Golden Gate. It’s also why the 1957 quake felt so different from the 1906 strike-slip motion.
Mussel Rock and the "Landslide" Problem
If you live near the coast in Daly City, you aren't just worrying about shaking. You're worrying about the ground disappearing. Mussel Rock is home to one of the largest active landslides in California.
There’s a legendary (and true) story about a municipal landfill sitting right on the fault zone there. It's a notoriously unstable area. When the 1906 quake hit, the epicenter was actually much closer to this spot than people originally thought. For decades, experts pointed to Point Reyes, but modern data suggests the "birthplace" of the 1906 disaster was likely right here, just off the Daly City coast.
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What a Major Quake Would Look Like Today
A repeat of the 1906 event (roughly a $7.9$ magnitude) would be a different beast in 2026. Back then, Daly City was mostly open space and pig farms. Today, it’s a densely packed suburb.
Recent risk assessments from San Mateo County and USGS scientists highlight three main threats:
- Liquefaction: In areas with soft soil or high water tables (like near Lake Merced), the ground can turn into a "soup" during intense shaking.
- Infrastructure Failure: We’re talking about broken gas mains and water lines. In 1957, a broken gas main caused a fire on Market Street in SF; today, the density makes that risk much higher.
- The "Crip" Factor: There is a constant "creep" along some fault segments, but the Daly City section is mostly "locked." This means it’s building up stress rather than letting it out in tiny bits.
Practical Steps for Living on the Line
You can't move the fault, but you can definitely move your bookshelf. Living in Daly City means being a bit more prepared than someone in, say, Indiana.
Secure your stuff. Spending $20 on metal straps for your water heater is the single best ROI you’ll ever get. If that thing tips over, you lose your emergency water supply and potentially start a fire.
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The "Drop, Cover, and Hold On" is real. Don't run outside. Most injuries happen from falling glass and facades. If you’re in bed, stay there and put a pillow over your head. If you’re at Mussel Rock or the beach and feel long shaking? Get to high ground immediately. A tsunami could follow within minutes.
Water is gold.
Store at least one gallon per person per day. If you run out, you can treat tap water with eight drops of regular household bleach per gallon, but having a three-day (or two-week) stash in the garage is better.
Daly City is a beautiful place with some of the best views in the Bay. But those views exist because of the massive tectonic forces beneath your feet. Respect the fault, secure your furniture, and keep your shoes under the bed.
Next Steps for You:
Check your home's proximity to the fault using the USGS Fault Map. If you live in a pre-1970s home, look into the "California Earthquake Brace + Bolt" program to see if you qualify for a retrofit grant.