Is Santa Clara County, California in an earthquake zone?

Santa Clara County sits in a very high seismic hazard area under the USGS National Seismic Hazard Model. Very strong ground shaking is expected over a building’s life. This is at or near a major active fault.

What is the Seismic Design Category for Santa Clara County?

USGS withholds a single Seismic Design Category here because ASCE 7-16 §11.4.8 requires a site-specific ground-motion study at this hazard level and site class.

Earthquake Risk in Santa Clara County, California: Seismic Hazard & Design Category (USGS)

Hazard level

Very high

Seismic Design Category

Site-specific study required

S_s (short period)

1.967 g

S₁ (1-second)

0.753 g

PGA

0.826 g

Values are for the county centroid (37.222, -121.690) at Site Class D, Risk Category II, ASCE 7-16. A specific parcel can differ, mostly because of soil.

What this means in Santa Clara County

Very strong ground shaking is expected over a building’s life. This is at or near a major active fault.

USGS withholds a single overall Seismic Design Category at this location. Under ASCE 7-16 §11.4.8 a site-specific ground-motion study is required at this combination of hazard and site class, so no single letter is reported. That is a requirement for more analysis, never a sign of lower risk.

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

Common next steps in a very high 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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