Butler's Seismic Design Category, explained

Under the seismic model IBC and ASCE 7 use for new construction, Butler is Category B. Low seismic hazard. Code requires basic seismic detailing (bracing, connections) but no special structural system restrictions. That puts Butler in the 26th percentile nationally for seismic hazard - higher than 26% of the 4,875 US cities USGS was checked against here.

How Butler compares

The raw figures: peak ground acceleration 0.045g, short-period spectral response 0.093g, 1-second spectral response 0.044g. Among 193 Pennsylvania cities in this dataset, Butler ranks 117 for seismic hazard, the 40th percentile within the state. About 13,010 people live in Butler, Pennsylvania.

What a retrofit costs in Butler

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

More on how this number was built

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