Metropolis's Seismic Design Category, explained

Under the seismic model IBC and ASCE 7 use for new construction, Metropolis 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 Metropolis in the 95th percentile nationally for seismic hazard - higher than 95% of the 4,875 US cities USGS was checked against here.

How Metropolis compares

The raw figures: peak ground acceleration 0.675g, short-period spectral response 1.104g, 1-second spectral response 0.369g. Among 330 Illinois cities in this dataset, Metropolis ranks 1 for seismic hazard, the 100th percentile within the state. About 5,776 people live in Metropolis, Illinois.

Retrofit economics for Metropolis

Outside California, no state-level retrofit grant equivalent to Brace + Bolt could be found for Illinois. A typical retrofit still runs $5,000-$10,000 nationally, about $7,000 for a common single-family job.

Earthquake insurance for a Metropolis home

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 Metropolis address.

More on how this number was built

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