The Cascadia subduction zone is one of the largest seismic-hazard features in the lower 48 — a 700-mile offshore fault running from Northern California through British Columbia. Major Cascadia events occur on the order of every 200–500 years. The last full-margin rupture was 1700, with sustained scientific evidence developed over the last several decades. For a Washington condo buyer, the question is not whether Cascadia is real — it is — but what the master policy covers if and when an event occurs, and what your personal exposure is in the meantime.

What Washington law requires

RCW 64.34.352 (1990 Condominium Act) requires condo associations to carry property insurance covering at least 80 percent of replacement value plus liability insurance. WUCIOA RCW 64.90.620 imposes similar requirements on post-2018 associations. RCW 64.38 (pre-2018 HOAs) is less prescriptive but most communities maintain master policies.

What none of these require:

• Earthquake coverage
• Seismic evaluations of existing buildings
• Retrofit of pre-modern-code construction
• Disclosure of seismic risk on resale

Earthquake coverage is a market decision. Given the cost — typically high premiums and 5–15 percent deductibles — many Washington associations decline it.

Reading the master policy for earthquake

Three patterns:

Earthquake explicitly excluded. Most common, especially for pre-2010 associations. The master policy covers fire, water damage, theft, liability — but excludes earthquake on the exclusions endorsement. Owners bear personal exposure for any uninsured association loss assessment that follows a seismic event.

Earthquake covered by separate endorsement on the master. The association has added an earthquake endorsement to the master policy. Read the deductible (often 5–15 percent of insured value), coverage limits (often capped well below standard property limits), and any named-event or co-insurance provisions. A 15-percent deductible on a $50 million building means the association absorbs $7.5 million before insurance pays — a sum typically passed back to owners through loss assessment.

Earthquake covered by separate standalone policy. Cleaner structure. The association maintains an independent earthquake policy alongside the all-risk master. Read both policies — deductibles, limits, and exclusions can differ.

Resale-certificate insurance disclosure

Washington's strong statutory resale-certificate regime helps here. RCW 64.34.425 requires the certificate to disclose insurance coverage including limits and deductibles. WUCIOA RCW 64.90.640 imposes parallel requirements. The certificate is binding on the association for the amounts disclosed.

Use the certificate to:

• Confirm whether earthquake coverage exists
• Verify the deductible structure
• Identify the carrier
• Use the 5-business-day rescission window if material concerns emerge

Construction era and seismic resilience

Washington building codes have evolved meaningfully:

• Pre-1970s. Predates significant seismic provisions. Unreinforced masonry common in older Seattle stock — among the highest seismic-vulnerability building types.
• 1970s through early 1990s. Improved but still under earlier provisions. Some retrofits voluntary; most have not been done.
• Mid-1990s onward. Stricter seismic codes. Better baseline resilience.
• Post-2010. Modern performance-based seismic design increasingly common in larger projects.

The diligence questions for an older Seattle high-rise:

• Construction type and structural system (steel frame, concrete, unreinforced masonry)
• Original construction date
• Any documented voluntary seismic retrofit history
• Master-policy earthquake treatment

Loss assessment and HO-6 sizing

The most likely personal seismic exposure is not your unit — it's the loss assessment that follows when association losses exceed insurance. Even a moderate event can generate per-unit loss assessments of $5,000–$50,000 or more depending on building damage and deductibles.

For your HO-6:

• Size loss-assessment coverage against realistic post-event exposure
• Confirm the policy covers earthquake-driven loss assessment specifically (some exclude it)
• Consider personal earthquake coverage if the association has none
• Discuss with your agent how loss-assessment coverage interacts with master-policy earthquake riders

What CondoSignal surfaces

We pull the resale certificate's insurance section, master-policy declarations page, exclusions endorsement, any voluntary seismic-evaluation reports, and construction-era documentation into a single state-specific risk summary. We flag earthquake exclusions, surplus-lines placements, and seismic-related minutes activity. The goal is to give Washington buyers a focused conversation with their lender, insurance agent, and counsel before closing — particularly around the loss-assessment exposure that surfaces when seismic events do occur.