Des Plaines, IL: what USGS's seismic model says
USGS's ASCE 7-16 seismic design model - the same standard building codes use - places Des Plaines in Seismic Design Category B: Low seismic hazard. Code requires basic seismic detailing (bracing, connections) but no special structural system restrictions. That puts Des Plaines in the 36th percentile nationally for seismic hazard - higher than 36% of the 4,875 US cities USGS was checked against here.
Des Plaines by the numbers
USGS's underlying values for Des Plaines: 0.059g peak ground acceleration, 0.117g at short period, 0.061g at 1 second. Within Illinois alone, Des Plaines ranks 248 of 330 cities by seismic hazard - the 25th percentile in-state. Des Plaines has a population of about 58,832.
What a retrofit costs in Des Plaines
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.
Insuring against this, not just retrofitting
A Des Plaines 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 Des Plaines's figures come from
Des Plaines'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 Des Plaines.