Does Carroll, IA need an earthquake retrofit?

Carroll 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. Rank it against the rest of the country and Carroll sits at the 16th percentile for seismic hazard among 4,875 US cities.

How Carroll compares

The raw figures: peak ground acceleration 0.028g, short-period spectral response 0.059g, 1-second spectral response 0.044g. Among 85 Iowa cities in this dataset, Carroll ranks 63 for seismic hazard, the 26th percentile within the state. About 10,125 people live in Carroll, Iowa.

What a retrofit costs in Carroll

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 Carroll address.

More on how this number was built

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