DeWitt's Seismic Design Category, explained

USGS's ASCE 7-16 seismic design model - the same standard building codes use - places DeWitt in Seismic Design Category B: Low seismic hazard. Code requires basic seismic detailing (bracing, connections) but no special structural system restrictions. That puts DeWitt in the 23th percentile nationally for seismic hazard - higher than 23% of the 4,875 US cities USGS was checked against here.

How DeWitt compares

The raw figures: peak ground acceleration 0.043g, short-period spectral response 0.088g, 1-second spectral response 0.061g. Among 85 Iowa cities in this dataset, DeWitt ranks 8 for seismic hazard, the 92th percentile within the state. About 5,620 people live in DeWitt, Iowa.

Bracing and bolting: the actual cost

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

Insuring against this, not just retrofitting

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 DeWitt address.

More on how this number was built

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