Mandan's Seismic Design Category, explained

Under the seismic model IBC and ASCE 7 use for new construction, Mandan is Category A. Lowest seismic design category. Building code requires no seismic-specific detailing here beyond ordinary construction practice. Rank it against the rest of the country and Mandan sits at the 7th percentile for seismic hazard among 4,875 US cities.

How Mandan compares

The raw figures: peak ground acceleration 0.024g, short-period spectral response 0.053g, 1-second spectral response 0.023g. Among 14 North Dakota cities in this dataset, Mandan ranks 10 for seismic hazard, the 31th percentile within the state. About 24,788 people live in Mandan, North Dakota.

Bracing and bolting: the actual cost

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

More on how this number was built

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