Great Falls's Seismic Design Category, explained

Great Falls carries Seismic Design Category B under USGS's ASCE 7-16 model. Low seismic hazard. Code requires basic seismic detailing (bracing, connections) but no special structural system restrictions. Nationally, Great Falls ranks above 49% of the 4,875 cities in this dataset for seismic hazard - the 49th percentile.

Great Falls by the numbers

The raw figures: peak ground acceleration 0.075g, short-period spectral response 0.159g, 1-second spectral response 0.067g. Among 19 Montana cities in this dataset, Great Falls ranks 13 for seismic hazard, the 33th percentile within the state. About 60,013 people live in Great Falls, Montana.

What a retrofit costs in Great Falls

Outside California, no state-level retrofit grant equivalent to Brace + Bolt could be found for Montana. A typical retrofit still runs $5,000-$10,000 nationally, about $7,000 for a common single-family job.

What this means for insurance

Outside California, earthquake coverage is typically sold as an endorsement added to a standard homeowners policy, not a separate product - worth asking about directly when getting a home-insurance quote for a Great Falls address.

More on how this number was built

The methodology guide covers exactly how USGS's public design-maps API produced Great Falls's numbers. The guide to what a Seismic Design Category actually means covers why a category is never a substitute for an engineer's assessment of one specific house.