Property teams, investors, buyers, insurers, developers, and operators comparing U.S. locations and territories.
Last reviewed: October 4, 2026
Lead with modeled ground motion
The earthquake module uses USGS National Seismic Hazard Model peak ground acceleration at selected return periods as its primary modeled signal. This provides location-specific variation even where FEMA NRI community context is unavailable.
- PGA is expressed as a fraction of gravity for the model's reference site condition.
- The report compares more frequent and rarer modeled ground-motion levels.
- The model describes probabilistic hazard; it does not predict when an earthquake will occur.
Read spectral acceleration as technical context
The report also shows spectral acceleration at short and longer structural periods. These values can help frame professional questions, but they are not converted into building-performance claims because the report does not know the structure's complete system and condition.
- Short- and longer-period values relate differently to structural response.
- The displayed values use the dataset reference site class and Vs30.
- A structural engineer should interpret project-specific design or retrofit implications.
Use community risk and mapped faults as support
FEMA NRI adds community-scale loss and exposure context, while USGS Quaternary faults add mapped proximity and classification evidence. Neither replaces the modeled shaking values or a site-specific investigation.
- A nearby mapped fault is relevant context, but distant sources can also produce strong shaking.
- Community expected annual loss is not a parcel or building loss estimate.
- Unavailable sources are excluded rather than interpreted as zero earthquake risk.
Know what still requires professional review
Local soils, liquefaction, slope stability, foundation type, building age, structural system, retrofit history, and code requirements remain outside a national screening score.
- Review local liquefaction, fault-rupture, and seismic-hazard maps where applicable.
- Confirm building construction, retrofit history, and adopted code era.
- Use geotechnical and structural professionals when the decision or signal warrants it.
Frequently asked questions
Does PGA predict damage to a building?
No. PGA describes modeled ground-motion hazard for a reference site condition. Damage depends on site response, structural system, age, condition, design, contents, and the actual earthquake.
Why are return periods shown?
Return periods express probabilistic hazard levels used for comparison. They do not mean an earthquake is scheduled to occur at that interval.
Does fault distance determine earthquake risk?
No. It is supporting context. Expected shaking depends on the full seismic-source and ground-motion model, which is why NSHM values lead the score.
TrueViewly reports are informational decision-support outputs based on available datasets and user-provided inputs. They are not certifications, legal advice, engineering opinions, insurance determinations, government approvals, or a replacement for official records and professional due diligence.