Vandalia, IL: what USGS's seismic model says

USGS's ASCE 7-16 seismic design model - the same standard building codes use - places Vandalia in Seismic Design Category D: High seismic hazard - this is the category most of coastal California, the Pacific Northwest, and other active fault regions fall into. Code mandates significant seismic detailing and restricts irregular structural configurations. This is the category the Brace + Bolt scope (cripple-wall bracing, foundation bolting) is built for. Nationally, Vandalia ranks above 83% of the 4,875 cities in this dataset for seismic hazard - the 83th percentile.

Where Vandalia sits in Illinois

The raw figures: peak ground acceleration 0.228g, short-period spectral response 0.405g, 1-second spectral response 0.148g. Among 330 Illinois cities in this dataset, Vandalia ranks 37 for seismic hazard, the 89th percentile within the state. About 7,358 people live in Vandalia, Illinois.

Bracing and bolting: the actual cost

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 Vandalia address.

More on how this number was built

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