Does Castle Shannon, PA need an earthquake retrofit?

Under the seismic model IBC and ASCE 7 use for new construction, Castle Shannon is Category B. Low seismic hazard. Code requires basic seismic detailing (bracing, connections) but no special structural system restrictions. Nationally, Castle Shannon ranks above 22% of the 4,875 cities in this dataset for seismic hazard - the 22th percentile.

Castle Shannon by the numbers

The raw figures: peak ground acceleration 0.042g, short-period spectral response 0.089g, 1-second spectral response 0.045g. Among 193 Pennsylvania cities in this dataset, Castle Shannon ranks 154 for seismic hazard, the 20th percentile within the state. About 8,094 people live in Castle Shannon, Pennsylvania.

Retrofit economics for Castle Shannon

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 Castle Shannon address.

More on how this number was built

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