Swarthmore's Seismic Design Category, explained

Swarthmore carries Seismic Design Category B under USGS's ASCE 7-16 model. Low seismic hazard. Code requires basic seismic detailing (bracing, connections) but no special structural system restrictions. Nationally, Swarthmore ranks above 56% of the 4,875 cities in this dataset for seismic hazard - the 56th percentile.

How Swarthmore compares

The raw figures: peak ground acceleration 0.101g, short-period spectral response 0.181g, 1-second spectral response 0.047g. Among 193 Pennsylvania cities in this dataset, Swarthmore ranks 27 for seismic hazard, the 86th percentile within the state. About 6,596 people live in Swarthmore, Pennsylvania.

Bracing and bolting: the actual cost

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 Swarthmore address.

More on how this number was built

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