Highwood's Seismic Design Category, explained

Under the seismic model IBC and ASCE 7 use for new construction, Highwood is Category B. Low seismic hazard. Code requires basic seismic detailing (bracing, connections) but no special structural system restrictions. That puts Highwood in the 31th percentile nationally for seismic hazard - higher than 31% of the 4,875 US cities USGS was checked against here.

Highwood by the numbers

USGS's underlying values for Highwood: 0.053g peak ground acceleration, 0.106g at short period, 0.058g at 1 second. Within Illinois alone, Highwood ranks 296 of 330 cities by seismic hazard - the 10th percentile in-state. Highwood has a population of about 5,358.

Retrofit economics for Highwood

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 Highwood 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 Highwood's figures come from

Highwood'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 Highwood.