Sonoma's Seismic Design Category, explained

USGS's ASCE 7-16 seismic design model - the same standard building codes use - places Sonoma in Seismic Design 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. Nationally, Sonoma ranks above 96% of the 4,875 cities in this dataset for seismic hazard - the 96th percentile.

How Sonoma compares

The raw figures: peak ground acceleration 0.736g, short-period spectral response 1.757g, 1-second spectral response 0.662g. Among 429 California cities in this dataset, Sonoma ranks 156 for seismic hazard, the 64th percentile within the state. About 10,606 people live in Sonoma, California.

Bracing and bolting: the actual cost

Because Sonoma is in California, the EBB grant applies if the ZIP code participates and the house qualifies (wood-framed house on a raised (not slab-on-grade) foundation, built before 1980): a $3,000-$7,000 bracing-and-bolting job drops to $0-$4,000 after the $3,000 base grant, or effectively free for income-eligible households getting the full $10,000.

Earthquake insurance for a Sonoma home

Earthquake coverage in California mostly runs through the California Earthquake Authority (CEA), sold only through licensed agents at CEA-participating insurers - there is no direct-to-consumer CEA policy. A general home-insurance quote is the practical starting point for a Sonoma homeowner asking about it.

More on how this number was built

The methodology guide covers exactly how USGS's public design-maps API produced Sonoma's numbers. The retrofit cost and grant guide covers every EBB eligibility rule, including the ones this page can't check.