Does Charleston, SC need an earthquake retrofit?

USGS's ASCE 7-16 seismic design model - the same standard building codes use - places 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. Rank it against the rest of the country and Charleston sits at the 98th percentile for seismic hazard among 4,875 US cities.

How Charleston compares

The raw figures: peak ground acceleration 1.02g, short-period spectral response 1.526g, 1-second spectral response 0.445g. Among 66 South Carolina cities in this dataset, Charleston ranks 6 for seismic hazard, the 92th percentile within the state. About 157,665 people live in Charleston, South Carolina.

What a retrofit costs in Charleston

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.

Insuring against this, not just retrofitting

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 Charleston address.

More on how this number was built

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