Does Chicago, IL need an earthquake retrofit?

Chicago 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. That puts Chicago in the 37th percentile nationally for seismic hazard - higher than 37% of the 4,875 US cities USGS was checked against here.

Chicago by the numbers

The raw figures: peak ground acceleration 0.06g, short-period spectral response 0.119g, 1-second spectral response 0.064g. Among 330 Illinois cities in this dataset, Chicago ranks 236 for seismic hazard, the 29th percentile within the state. About 2,721,308 people live in Chicago, 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 Chicago address.

More on how this number was built

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