Does Brookings, SD need an earthquake retrofit?

Under the seismic model IBC and ASCE 7 use for new construction, Brookings is Category A. Lowest seismic design category. Building code requires no seismic-specific detailing here beyond ordinary construction practice. Nationally, Brookings ranks above 14% of the 4,875 cities in this dataset for seismic hazard - the 14th percentile.

Where Brookings sits in South Dakota

The raw figures: peak ground acceleration 0.043g, short-period spectral response 0.088g, 1-second spectral response 0.026g. Among 18 South Dakota cities in this dataset, Brookings ranks 15 for seismic hazard, the 18th percentile within the state. About 24,555 people live in Brookings, South Dakota.

Bracing and bolting: the actual cost

Outside California, no state-level retrofit grant equivalent to Brace + Bolt could be found for South Dakota. 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 Brookings address.

More on how this number was built

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