Polk City, IA: what USGS's seismic model says

Under the seismic model IBC and ASCE 7 use for new construction, Polk City is Category B. Low seismic hazard. Code requires basic seismic detailing (bracing, connections) but no special structural system restrictions. Nationally, Polk City ranks above 16% of the 4,875 cities in this dataset for seismic hazard - the 16th percentile.

Where Polk City sits in Iowa

USGS's underlying values for Polk City: 0.029g peak ground acceleration, 0.06g at short period, 0.05g at 1 second. Within Iowa alone, Polk City ranks 56 of 85 cities by seismic hazard - the 35th percentile in-state. Polk City has a population of about 6,430.

What a retrofit costs in Polk City

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 Iowa 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 Iowa.

What this means for insurance

A Polk City 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 Polk City's figures come from

Polk City'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 Polk City.