What is the Seismic Design Category for Big Horn County?

Around the county centre the ASCE 7-16 Seismic Design Category is B, assuming Site Class D. The category for a specific parcel depends on its soil.

Earthquake Risk in Big Horn County, Montana: Seismic Hazard & Design Category (USGS)

Q: Is Big Horn County, Montana in an earthquake zone?

Big Horn County sits in a low seismic hazard area under the USGS National Seismic Hazard Model. Damaging earthquakes are infrequent here, but "low" is not "zero". The New Madrid and Charleston events both struck areas that look like this on a hazard map.

Hazard level

Low

Seismic Design Category

S_s (short period)

0.15 g

S₁ (1-second)

0.051 g

PGA

0.077 g

Values are for the county centroid (45.408, -107.518) at Site Class D, Risk Category II, ASCE 7-16. A specific parcel can differ, mostly because of soil.

What this means in Big Horn County

Damaging earthquakes are infrequent here, but "low" is not "zero". The New Madrid and Charleston events both struck areas that look like this on a hazard map.

Buildings here are designed to Seismic Design Category B, which is how U.S. codes classify earthquake demand on a site. It drives structural detailing, bracing and, in the higher categories, whether a site-specific ground-motion study is needed at all.

Check a specific address in Big Horn County County-centre values are a starting point. The free lookup runs the model at your exact address.

Common next steps in a low hazard area

Anchor the heavy things. Tall furniture, water heaters and wall-mounted screens move first in shaking.
→ Anti-tip furniture straps and anchors
Know how to shut off the gas. The wrench belongs at the meter, not in a drawer indoors.
→ Non-sparking gas shut-off wrench
Keep water you did not have to think about. Mains can be out for days after a significant event.
→ Emergency water storage and kits

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