Does Manhattan, IL need an earthquake retrofit?

Under the seismic model IBC and ASCE 7 use for new construction, Manhattan is Category B. Low seismic hazard. Code requires basic seismic detailing (bracing, connections) but no special structural system restrictions. Rank it against the rest of the country and Manhattan sits at the 43th percentile for seismic hazard among 4,875 US cities.

Where Manhattan sits in Illinois

The raw figures: peak ground acceleration 0.068g, short-period spectral response 0.134g, 1-second spectral response 0.07g. Among 330 Illinois cities in this dataset, Manhattan ranks 114 for seismic hazard, the 66th percentile within the state. About 10,772 people live in Manhattan, Illinois.

What a retrofit costs in Manhattan

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 Manhattan address.

More on how this number was built

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