St. Charles's Seismic Design Category, explained

St. Charles 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. Nationally, St. Charles ranks above 81% of the 4,875 cities in this dataset for seismic hazard - the 81th percentile.

How St. Charles compares

USGS's underlying values for St. Charles: 0.185g peak ground acceleration, 0.344g at short period, 0.139g at 1 second. Within Missouri alone, St. Charles ranks 56 of 135 cities by seismic hazard - the 59th percentile in-state. St. Charles has a population of about 72,458.

What a retrofit costs in St. Charles

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 St. Charles 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 St. Charles's figures come from

St. Charles'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 St. Charles.