Alpena's Seismic Design Category, explained

Under the seismic model IBC and ASCE 7 use for new construction, Alpena is Category A. Lowest seismic design category. Building code requires no seismic-specific detailing here beyond ordinary construction practice. That puts Alpena in the 9th percentile nationally for seismic hazard - higher than 9% of the 4,875 US cities USGS was checked against here.

Where Alpena sits in Michigan

The raw figures: peak ground acceleration 0.027g, short-period spectral response 0.058g, 1-second spectral response 0.027g. Among 153 Michigan cities in this dataset, Alpena ranks 139 for seismic hazard, the 9th percentile within the state. About 10,116 people live in Alpena, Michigan.

Bracing and bolting: the actual cost

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

More on how this number was built

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