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California: Risks & Trends

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Same standard as every other page on this site: every figure below is independently sourced, and figures that vary across sources, or measure genuinely different things, are flagged as such rather than collapsed into one number that looks more precise than the underlying data actually supports.

Earthquake probability: UCERF3 and the ShakeOut scenario

MetricFigureSource
30-yr chance of M6.7+, Los Angeles region 60% USGS / UCERF3
30-yr chance of M6.7+, San Francisco Bay region 72% USGS / UCERF3
30-yr chance of M7.0+, Los Angeles region 46% USGS / UCERF3
30-yr chance of M7.0+, San Francisco Bay region 51% USGS / UCERF3
ShakeOut planning scenario magnitude M7.8, southern San Andreas USGS
Projected deaths, ShakeOut scenario ~1,800 USGS
Projected injuries, ShakeOut scenario ~50,000 USGS
Projected economic losses, ShakeOut scenario >$200 billion USGS

Why the LA and Bay Area numbers differ, and what 'UCERF3' actually covers

These percentages count every fault capable of producing that magnitude in each region, not just the San Andreas alone, which is why the Bay Area’s figure is higher despite the San Andreas itself running directly through Los Angeles’s broader region too: the Bay Area’s fault network (San Andreas, Hayward, Calaveras, and others) produces a higher combined probability across all sources considered together.

The January 2025 Southern California firestorm

MetricFigure
Confirmed deaths, all fires combined 31
Separately estimated total mortality (direct + indirect, one epidemiological study) ~440
Total acres burned, all fires ~57,500
Structures destroyed or damaged, all fires 18,189+
Palisades Fire: deaths / acres / structures 12 / 23,448 / 7,854 destroyed or damaged
Eaton Fire: deaths / acres / structures 18 / 14,021 / 10,491 destroyed or damaged

The 31-versus-440 gap is not a data error

The 31 figure is the confirmed direct death toll, people who died from the fires themselves. The roughly 440 figure comes from a separate epidemiological study estimating total attributable mortality, deaths from smoke exposure, disrupted medical care, and other indirect effects layered on top of the direct toll, not a revision or correction of the confirmed count. Both numbers are real and both are useful, but they measure different things, and citing one without the other’s context risks a misleading impression either way.

Two things stand out from the fire-by-fire breakdown: the Eaton Fire killed more people despite burning fewer acres than the Palisades Fire, and the Palisades Fire, while smaller in structures lost than Eaton, is specifically the most destructive fire in the city of Los Angeles’s own history, a distinct record from the county- or state-wide totals.

What these two have in common

Both of California’s defining risks share a structural feature this manual’s own framing is built around: they’re not single, bounded events with a clear before-and-after, they’re standing conditions of living in the state’s major population centers. A magnitude 6.7+ earthquake in the Bay Area or LA region isn’t a remote possibility on a 500-year timescale, it’s a better-than-even chance within 30 years by the state’s own modeling; a wind-driven wildfire capable of the January 2025 event’s speed and scale isn’t confined to remote wildland, it reached deep into dense Los Angeles neighborhoods with hours of warning at most.

Sources