Manchester's Seismic Design Category, explained

Under the seismic model IBC and ASCE 7 use for new construction, Manchester is Category C. Moderate seismic hazard. Code adds irregular-building restrictions and requires bracing of some nonstructural components (e.g. tall shelving, water heaters) in addition to structural detailing. Nationally, Manchester ranks above 79% of the 4,875 cities in this dataset for seismic hazard - the 79th percentile.

How Manchester compares

USGS's underlying values for Manchester: 0.283g peak ground acceleration, 0.429g at short period, 0.085g at 1 second. Within New Hampshire alone, Manchester ranks 1 of 13 cities by seismic hazard - the 100th percentile in-state. Manchester has a population of about 116,386.

Bracing and bolting: the actual cost

A full earthquake retrofit typically runs $5,000-$10,000 nationally (around $7,000 typical), driven mainly by house size and foundation type, not by New Hampshire specifically. California's Earthquake Brace + Bolt grant, which covers a large share of this cost, is a California-only program and does not apply in New Hampshire.

What this means for insurance

A Manchester homeowner cannot buy a standalone earthquake policy in most cases - it is added to an existing homeowners policy as an endorsement, so the place to start is a regular home-insurance quote.

Where Manchester's figures come from

Manchester's Category C and every number above trace to USGS's own ASCE 7-16 Design Maps service - see the methodology guide. See the category explainer for what Category C does and doesn't tell you about Manchester.