Jerseyville's Seismic Design Category, explained

Under the seismic model IBC and ASCE 7 use for new construction, Jerseyville is Category C. Moderate seismic hazard. Code adds irregular-building restrictions and requires bracing of some nonstructural components (e.g. tall shelving, water heaters) in addition to structural detailing. Rank it against the rest of the country and Jerseyville sits at the 74th percentile for seismic hazard among 4,875 US cities.

Where Jerseyville sits in Illinois

The raw figures: peak ground acceleration 0.146g, short-period spectral response 0.283g, 1-second spectral response 0.125g. Among 330 Illinois cities in this dataset, Jerseyville ranks 46 for seismic hazard, the 86th percentile within the state. About 8,350 people live in Jerseyville, Illinois.

What a retrofit costs in Jerseyville

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

More on how this number was built

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