Does Irmo, SC need an earthquake retrofit?

Irmo carries Seismic Design Category C under USGS's ASCE 7-16 model. Moderate seismic hazard. Code adds irregular-building restrictions and requires bracing of some nonstructural components (e.g. tall shelving, water heaters) in addition to structural detailing. Nationally, Irmo ranks above 77% of the 4,875 cities in this dataset for seismic hazard - the 77th percentile.

How Irmo compares

The raw figures: peak ground acceleration 0.195g, short-period spectral response 0.344g, 1-second spectral response 0.11g. Among 66 South Carolina cities in this dataset, Irmo ranks 28 for seismic hazard, the 58th percentile within the state. About 12,086 people live in Irmo, South Carolina.

What a retrofit costs in Irmo

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.

What this means for insurance

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 Irmo address.

More on how this number was built

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