Earthquake readiness — California, Pacific Northwest, and the Cascadia subduction zone, ranked by what households should actually do

The three earthquake-risk regions

US earthquake risk concentrates in three regions:

• California (San Andreas + adjacent faults): Highest-frequency moderate-magnitude risk. Magnitude 6+ events occur multiple times per decade. Cities at significant risk: San Francisco Bay Area, Los Angeles metro, San Diego.
• Pacific Northwest (Cascadia subduction zone): Lower frequency but highest magnitude potential. Magnitude 9+ "Cascadia Megathrust" events occur every 200-500 years. Last in 1700 — averages suggest one is geologically overdue. Cities at risk: Portland, Seattle, Vancouver.
• Alaska (multiple faults): Frequent moderate-magnitude events, low population density limits household impact except in Anchorage.

For US households living outside these three regions, earthquake risk is low enough that the actions below are unnecessary. For households inside any of the three regions, the actions matter.

Five actions ranked by leverage

1. Secure heavy furniture to walls (highest leverage, lowest cost)

Most earthquake injuries are not from buildings collapsing — they are from heavy furniture falling on people during shaking. Bookshelves, tall dressers, TVs, water heaters, refrigerators.

Anchoring kits cost $10-30 per item at any hardware store. Time to install: 30-60 minutes per item.

For a 2,000-sq-ft home, securing 4-6 critical items takes one Saturday morning and approximately $80-180. Single highest-leverage earthquake action.

2. Build the 7-day water supply

In a Cascadia Megathrust event, water infrastructure could be offline for 7-30 days. In a California 6.0+ event, water infrastructure could be offline for 2-7 days.

7 days × 1 gallon per person per day = 7 gallons per person minimum. Stored in 5-gallon BPA-free water jugs or factory-sealed water bottles.

For family of 4: 28 gallons. Cost $20-40 at any grocery store. Rotate annually.

3. Stock 7-14 days of shelf-stable food

Food infrastructure recovers faster than water in earthquake scenarios — typically 2-5 days. But you need to be self-sufficient during that window.

7 days of food per household member: canned protein, peanut butter, dried fruit, crackers, energy bars, instant rice/pasta, peanut butter, oats. ~$60-100 per person.

4. Secure documents and pre-pack evacuation bag

Earthquake scenarios may require evacuation if your home is unsafe. Pre-packed bag:

• Documents (passport, driver's license, insurance card, deed)
• Phone charger + battery pack
• Cash $200-500 in small bills
• Change of clothes per person
• Sturdy shoes (you may need to walk over debris)
• 7-day medication supply
• N95 masks (dust from collapsed structures is significant)
• Whistle (helps rescuers locate you if trapped)

Cost: $50-100 if buying new bag and contents. Time: 1-2 hours.

5. Verify gas shutoff capability

In a major earthquake, gas line breaks and resulting fires are a leading cause of post-earthquake property damage. Your home's main gas shutoff is typically at the meter outside the house.

Verify: - You know where it is - You have a wrench appropriate to your meter (different regions use different valves) - Every adult household member knows how to operate it - The wrench is stored near the meter (not in a tool box you might lose access to)

Shut off ONLY if you smell gas after an event. Closing it unnecessarily requires a utility callout to safely reopen.

Region-specific notes

California

The 1989 Loma Prieta (Magnitude 6.9) and 1994 Northridge (Magnitude 6.7) events produced 60-70 fatalities each, primarily from collapsed structures and fires. Modern California building codes have substantially reduced collapse risk. Older buildings (pre-1980) still represent significant residential risk in known fault zones.

For California residents: the building you live in matters more than your actions during shaking. Older buildings + soft-story construction = elevated risk.

Pacific Northwest

The 1700 Cascadia event produced widespread devastation across what is now Oregon, Washington, and northern California. Tsunami waves were recorded as far as Japan.

If a Cascadia Megathrust event occurs, infrastructure damage will be regional, not local. 30-day timeline for full recovery. Households in this region need substantially deeper preparedness — 14-21 days of supplies, not 7. Plus tsunami awareness for coastal locations (10-30 minutes warning maximum).

Alaska

Anchorage households should follow California-level preparedness. Rural Alaska households face longer infrastructure recovery times due to logistics; 14-21 day supplies more appropriate.

What this is not

This is not advice to live in fear of earthquake. The probability of a significant earthquake event affecting any specific household in any year is low — even in the three high-risk regions. The five actions above are not panic preparation; they are calibrated household maintenance for the three risk regions.

The single most-leveraged action is securing heavy furniture. Total cost $80-180 for typical household. Total time one Saturday morning. Massively reduces injury risk in the most likely event (moderate-magnitude shaking).

One thing this week: if you live in California, Oregon, Washington, or Alaska — look at your tallest piece of furniture. Is it anchored to the wall? If no, buy an anchoring kit at your hardware store this Saturday. 30-minute installation. Highest-leverage earthquake action.

— Systems Fail Lab