One USGS service, city by city

Every city page reports live output from USGS's ASCE 7-16 Design Maps web service (earthquake.usgs.gov/ws/designmaps), queried at that city's own coordinates with riskCategory=II (standard occupancy) and siteClass=D (stiff soil - the standard default absent a site-specific geotechnical report), the same baseline assumptions IBC and ASCE 7 use when neither is known.

What the two Categories mean, and which one wins

ASCE 7 computes two Seismic Design Categories per site - one from the short-period value, one from the 1-second value - and requires using whichever is MORE SEVERE as the governing category. When the 1-second category comes back blank, that's USGS flagging that a site-specific study is required under §11.4.8, not missing data; Los Angeles, CA is one such city.

How the national rank is built

Cities are ranked first by governing Seismic Design Category (most severe first, with the beyond-standard-tables cities ranked above even Category F) and then by peak ground acceleration, to give every city its own position rather than large tied groups within a 6-category scale.

Where the cost and grant figures come from

Retrofit cost ranges are sourced from multiple 2026 contractor-cost guides (Fixr.com, HomeAdvisor, Angi), cross-checked against Bay-Area-specific figures for the bracing-and-bolting scope specifically. California's Earthquake Brace + Bolt grant terms come from the program's own published rules. Neither varies by city - cost is driven by the house, not the address, so this site reports one national range rather than inventing a city-level number the data doesn't support.

Where to go next

See the range this plays out across: Caruthersville, MO, Noblesville, IN, Marathon, FL.

What a Seismic Design Category Actually Means (and Doesn't) · Earthquake Retrofit Cost and California's Brace + Bolt Grant, in Full