From Alaska’s monster quakes to California’s infamous ruptures, the U.S. has seen some of the world’s most destructive seismic events.
The question isn’t whether another “Big One” will hit — it’s when, and where.
Here’s the history, the science, and the predictions that matter.
1964 Great Alaska Earthquake
Magnitude 9.2, the strongest in U.S. history. Shook for 4.5 minutes, unleashed tsunamis, killed 130+, and reshaped Alaska’s landscape.
1700 Cascadia Quake
Estimated magnitude 8.7–9.2 off the Pacific Northwest. Sent a tsunami all the way to Japan. Oral histories and geological evidence match up — proof of America’s hidden monster fault.
Aleutian Giants
1957 Andreanof Islands (M 8.6) and 1965 Rat Islands (M 8.7) — remote but powerful. Triggered Pacific-wide tsunamis, reminders that Alaska dominates the top of the charts.
San Francisco 1906
Magnitude 7.9. Fires consumed the city after the quake. More than 3,000 dead — still the deadliest U.S. earthquake on record.
Why It Matters Now
- California’s San Andreas is locked and loaded.
- Cascadia Subduction Zone hasn’t ruptured since 1700.
- Both regions show strain building, with odds that make seismologists nervous.
California Forecasts
- 72% chance of a M ≥ 6.7 quake in the San Francisco Bay Area within 30 years.
- ~7% chance of a M ≥ 8 statewide over the same period.
- Translation: damaging quakes in California aren’t just possible, they’re near certain.
Cascadia Forecasts
- ~10–15% chance of a M 9 full-margin rupture in the next 50 years.
- ~37% chance of a partial M 8+ event in the same window.
- Recurrence interval: ~500 years. It’s been 325 years since the last one.
The Century Horizon
- Cascadia “Big One” odds by 2100: ~25–35%.
- California megaquake (M ≥ 8) odds by 2100: ~15–20%.
- Smaller but still destructive quakes (M 7–7.9) remain highly likely across both zones.
What’s at Stake
- Millions at risk across the West Coast.
- Billions in economic damage possible in a single event.
- Critical infrastructure — ports, pipelines, power — all in the quake zones.
Bottom Line
Alaska’s past proves the U.S. can shake harder than almost anywhere. California and Cascadia’s future shows we’re not done yet. The “Big One” isn’t a question of if — it’s a matter of odds, timelines, and preparation.
