Belleville's Seismic Design Category, explained

USGS's ASCE 7-16 seismic design model - the same standard building codes use - places Belleville 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, Belleville ranks above 85% of the 4,875 cities in this dataset for seismic hazard - the 85th percentile.

How Belleville compares

The raw figures: peak ground acceleration 0.295g, short-period spectral response 0.505g, 1-second spectral response 0.174g. Among 330 Illinois cities in this dataset, Belleville ranks 19 for seismic hazard, the 95th percentile within the state. About 40,560 people live in Belleville, Illinois.

Retrofit economics for Belleville

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.

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 Belleville address.

More on how this number was built

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