Oak Forest's Seismic Design Category, explained

Under the seismic model IBC and ASCE 7 use for new construction, Oak Forest is Category B. Low seismic hazard. Code requires basic seismic detailing (bracing, connections) but no special structural system restrictions. That puts Oak Forest in the 41th percentile nationally for seismic hazard - higher than 41% of the 4,875 US cities USGS was checked against here.

Oak Forest by the numbers

USGS's underlying values for Oak Forest: 0.064g peak ground acceleration, 0.127g at short period, 0.067g at 1 second. Within Illinois alone, Oak Forest ranks 147 of 330 cities by seismic hazard - the 56th percentile in-state. Oak Forest has a population of about 26,813.

What a retrofit costs in Oak Forest

A full earthquake retrofit typically runs $5,000-$10,000 nationally (around $7,000 typical), driven mainly by house size and foundation type, not by Illinois specifically. California's Earthquake Brace + Bolt grant, which covers a large share of this cost, is a California-only program and does not apply in Illinois.

What this means for insurance

A Oak Forest homeowner cannot buy a standalone earthquake policy in most cases - it is added to an existing homeowners policy as an endorsement, so the place to start is a regular home-insurance quote.

Where Oak Forest's figures come from

Oak Forest's Category B and every number above trace to USGS's own ASCE 7-16 Design Maps service - see the methodology guide. See the category explainer for what Category B does and doesn't tell you about Oak Forest.