Earthquake Risk Assessment
Understand seismic hazards, fault line proximity, and structural risks for your property
Check Earthquake Risk for Your Address
What is Earthquake Risk?
Earthquake risk measures the probability of ground shaking and potential structural damage at a specific location. The United States Geological Survey (USGS) assesses seismic hazards based on:
- Proximity to fault lines: Distance from active earthquake faults
- Historical seismic activity: Earthquake frequency and magnitude over time
- Soil and bedrock composition: Ground types that amplify or dampen shaking
- Peak Ground Acceleration (PGA): Expected ground motion intensity
- Building age and construction: Structural vulnerability to shaking
Peak Ground Acceleration (PGA)
PGA measures the maximum ground acceleration during an earthquake as a percentage of gravity (g). A PGA of 0.1g means the ground accelerates at 10% of Earth's gravitational force. Higher PGA values indicate stronger shaking and greater damage potential.
Why Earthquake Risk Matters for Homeowners
Earthquake risk significantly affects homeownership in several ways:
- Structural safety: Unreinforced buildings can collapse during major earthquakes
- Insurance costs: Earthquake insurance is expensive in high-risk zones
- Property values: Homes near fault lines may have lower resale value
- Retrofit requirements: Some cities mandate seismic retrofitting for older buildings
- Utility disruption: Earthquakes can damage water, gas, and electrical systems
Earthquake Risk Zones
Very High Risk
Areas with frequent earthquakes and major fault lines
Coastal California, San Francisco Bay Area, Los Angeles Basin
High Risk
Significant earthquake probability and potential damage
Pacific Northwest, Alaska, parts of Nevada and Utah
Moderate Risk
Occasional earthquakes, moderate damage potential
Parts of Missouri, South Carolina, Idaho, Montana
Low Risk
Rare earthquakes, minimal damage expected
Most of the Eastern US, Midwest, and Gulf Coast
Major US Fault Lines
San Andreas Fault
California
800 miles
Very High - Major quake overdue
Cascadia Subduction Zone
Pacific Northwest
600 miles
Very High - Megaquake potential
Hayward Fault
San Francisco Bay Area
74 miles
Very High - Urban area impact
New Madrid Fault
Central Mississippi Valley
150 miles
High - Large quakes in 1811-1812
The "Big One": Seismologists predict a 70% probability of a magnitude 6.7 or larger earthquake striking the San Francisco Bay Area before 2030. The Cascadia Subduction Zone could produce a magnitude 9.0 megaquake that would affect millions in the Pacific Northwest.
How We Measure Earthquake Risk
USGS Seismic Hazard Maps
The USGS National Seismic Hazard Model provides probabilistic ground motion values for the entire United States. These maps show the likelihood of experiencing specific levels of ground shaking over 50-year periods.
Fault Proximity Analysis
We calculate distance from your property to known active faults. Properties within 1 mile of active faults face significantly higher risk than those farther away.
Soil Amplification Factors
Soft soils can amplify earthquake shaking by 2-4 times compared to bedrock. We analyze soil composition to assess amplification risk.
Historical Earthquake Data
We review earthquake frequency, magnitude, and recurrence intervals in your area using USGS historical data and scientific research.
Earthquake Mitigation Strategies
Reduce earthquake damage with these structural improvements and safety measures
Foundation Bolting
Secure the house to its foundation with anchor bolts to prevent sliding or toppling during ground shaking.
Cripple Wall Bracing
Reinforce short walls between foundation and first floor to prevent collapse.
Soft Story Retrofitting
Strengthen buildings with weak first floors (garages, large openings) to prevent collapse.
Chimney Bracing
Secure unreinforced masonry chimneys that can collapse during earthquakes.
Water Heater Strapping
Strap water heaters to walls to prevent tipping and gas line ruptures.
Automatic Gas Shutoff
Install earthquake-activated gas shutoff valves to prevent fires.
Retrofit Tax Benefits: Many local governments offer tax credits, grants, or low-interest loans for seismic retrofitting. California's Earthquake Brace + Bolt program provides up to $3,000 in rebates for qualifying homes.
Earthquake Risk Tips for Homebuyers
1. Check Construction Date and Type
Homes built before 1980 (before modern seismic codes) are much more vulnerable. Wood-frame houses perform better than unreinforced masonry or concrete.
2. Request Seismic Inspection
Hire a structural engineer or seismic specialist to assess the home's earthquake resistance and identify needed retrofits.
3. Get Earthquake Insurance Quotes
Earthquake damage is NOT covered by standard homeowners insurance. Get quotes from the California Earthquake Authority (CEA) or private insurers before buying.
4. Review Seller Disclosures
Ask about previous earthquake damage, retrofitting work, and proximity to known faults. In California, sellers must disclose if property is in a seismic hazard zone.
5. Budget for Retrofitting
Plan to spend $5,000-$15,000 for basic retrofits on older homes. Soft-story buildings may require $60,000+ in improvements.
Check All Climate Risks for Your Property
Earthquake is just one of six climate risk factors we track