Broomfield's Seismic Design Category, explained

Under the seismic model IBC and ASCE 7 use for new construction, Broomfield is Category B. Low seismic hazard. Code requires basic seismic detailing (bracing, connections) but no special structural system restrictions. Nationally, Broomfield ranks above 59% of the 4,875 cities in this dataset for seismic hazard - the 59th percentile.

Broomfield by the numbers

The raw figures: peak ground acceleration 0.113g, short-period spectral response 0.207g, 1-second spectral response 0.058g. Among 79 Colorado cities in this dataset, Broomfield ranks 42 for seismic hazard, the 47th percentile within the state. About 78,323 people live in Broomfield, Colorado.

Retrofit economics for Broomfield

Outside California, no state-level retrofit grant equivalent to Brace + Bolt could be found for Colorado. 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 Broomfield address.

More on how this number was built

The methodology guide covers exactly how USGS's public design-maps API produced Broomfield'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.