North Charleston's Seismic Design Category, explained

USGS's ASCE 7-16 seismic design model - the same standard building codes use - places North Charleston 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. That puts North Charleston in the 98th percentile nationally for seismic hazard - higher than 98% of the 4,875 US cities USGS was checked against here.

North Charleston by the numbers

The raw figures: peak ground acceleration 1.276g, short-period spectral response 1.884g, 1-second spectral response 0.552g. Among 66 South Carolina cities in this dataset, North Charleston ranks 1 for seismic hazard, the 100th percentile within the state. About 126,005 people live in North Charleston, South Carolina.

Bracing and bolting: the actual cost

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

Earthquake insurance for a North Charleston 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 North Charleston address.

More on how this number was built

The methodology guide covers exactly how USGS's public design-maps API produced North Charleston'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.