Columbia's Seismic Design Category, explained

USGS's ASCE 7-16 seismic design model - the same standard building codes use - places Columbia in Seismic Design Category D: 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, Columbia ranks above 85% of the 4,875 cities in this dataset for seismic hazard - the 85th percentile.

How Columbia compares

The raw figures: peak ground acceleration 0.288g, short-period spectral response 0.495g, 1-second spectral response 0.172g. Among 330 Illinois cities in this dataset, Columbia ranks 22 for seismic hazard, the 94th percentile within the state. About 10,919 people live in Columbia, Illinois.

What a retrofit costs in Columbia

Outside California, no state-level retrofit grant equivalent to Brace + Bolt could be found for Illinois. A typical retrofit still runs $5,000-$10,000 nationally, about $7,000 for a common single-family job.

Earthquake insurance for a Columbia home

Outside California, earthquake coverage is typically sold as an endorsement added to a standard homeowners policy, not a separate product - worth asking about directly when getting a home-insurance quote for a Columbia address.

More on how this number was built

The methodology guide covers exactly how USGS's public design-maps API produced Columbia's numbers. The guide to what a Seismic Design Category actually means covers why a category is never a substitute for an engineer's assessment of one specific house.