O'Fallon's Seismic Design Category, explained

O'Fallon carries Seismic Design Category D under USGS's ASCE 7-16 model. High seismic hazard - this is the category most of coastal California, the Pacific Northwest, and other active fault regions fall into. Code mandates significant seismic detailing and restricts irregular structural configurations. This is the category the Brace + Bolt scope (cripple-wall bracing, foundation bolting) is built for. That puts O'Fallon in the 80th percentile nationally for seismic hazard - higher than 80% of the 4,875 US cities USGS was checked against here.

O'Fallon by the numbers

USGS's underlying values for O'Fallon: 0.165g peak ground acceleration, 0.314g at short period, 0.134g at 1 second. Within Missouri alone, O'Fallon ranks 63 of 135 cities by seismic hazard - the 54th percentile in-state. O'Fallon has a population of about 95,355.

Bracing and bolting: the actual cost

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 Missouri 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 Missouri.

Insuring against this, not just retrofitting

A O'Fallon 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 O'Fallon's figures come from

O'Fallon's Category D 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 D does and doesn't tell you about O'Fallon.