Missoula's Seismic Design Category, explained

USGS's ASCE 7-16 seismic design model - the same standard building codes use - places Missoula in Seismic Design Category D: High seismic hazard - this is the category most of coastal California, the Pacific Northwest, and other active fault regions fall into. Code mandates significant seismic detailing and restricts irregular structural configurations. This is the category the Brace + Bolt scope (cripple-wall bracing, foundation bolting) is built for. Nationally, Missoula ranks above 81% of the 4,875 cities in this dataset for seismic hazard - the 81th percentile.

Missoula by the numbers

USGS's underlying values for Missoula: 0.187g peak ground acceleration, 0.422g at short period, 0.141g at 1 second. Within Montana alone, Missoula ranks 10 of 19 cities by seismic hazard - the 50th percentile in-state. Missoula has a population of about 78,204.

Retrofit economics for Missoula

A full earthquake retrofit typically runs $5,000-$10,000 nationally (around $7,000 typical), driven mainly by house size and foundation type, not by Montana specifically. California's Earthquake Brace + Bolt grant, which covers a large share of this cost, is a California-only program and does not apply in Montana.

Insuring against this, not just retrofitting

A Missoula homeowner cannot buy a standalone earthquake policy in most cases - it is added to an existing homeowners policy as an endorsement, so the place to start is a regular home-insurance quote.

Where Missoula's figures come from

Missoula's Category D and every number above trace to USGS's own ASCE 7-16 Design Maps service - see the methodology guide. See the category explainer for what Category D does and doesn't tell you about Missoula.