Does Hanahan, SC need an earthquake retrofit?

Under the seismic model IBC and ASCE 7 use for new construction, Hanahan is 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 Hanahan in the 98th percentile nationally for seismic hazard - higher than 98% of the 4,875 US cities USGS was checked against here.

How Hanahan compares

The raw figures: peak ground acceleration 1.186g, short-period spectral response 1.757g, 1-second spectral response 0.515g. Among 66 South Carolina cities in this dataset, Hanahan ranks 4 for seismic hazard, the 95th percentile within the state. About 21,983 people live in Hanahan, South Carolina.

Retrofit economics for Hanahan

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 Hanahan address.

More on how this number was built

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