Does South Holland, IL need an earthquake retrofit?

Under the seismic model IBC and ASCE 7 use for new construction, South Holland 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 South Holland sits at the 38th percentile for seismic hazard among 4,875 US cities.

South Holland by the numbers

The raw figures: peak ground acceleration 0.061g, short-period spectral response 0.122g, 1-second spectral response 0.066g. Among 330 Illinois cities in this dataset, South Holland ranks 224 for seismic hazard, the 32th percentile within the state. About 20,775 people live in South Holland, Illinois.

What a retrofit costs in South Holland

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.

Earthquake insurance for a South Holland home

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 South Holland address.

More on how this number was built

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