Does West Chicago, IL need an earthquake retrofit?

Under the seismic model IBC and ASCE 7 use for new construction, West Chicago is Category B. Low seismic hazard. Code requires basic seismic detailing (bracing, connections) but no special structural system restrictions. That puts West Chicago in the 44th percentile nationally for seismic hazard - higher than 44% of the 4,875 US cities USGS was checked against here.

How West Chicago compares

The raw figures: peak ground acceleration 0.068g, short-period spectral response 0.132g, 1-second spectral response 0.065g. Among 330 Illinois cities in this dataset, West Chicago ranks 108 for seismic hazard, the 67th percentile within the state. About 25,469 people live in West Chicago, Illinois.

What a retrofit costs in West Chicago

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 West Chicago address.

More on how this number was built

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