PlainQuake

Interactive tool

Earthquake Risk Calculator

Select a US state to assess its earthquake risk from 20 years of USGS ComCat data, historical counts, maximum magnitude, yearly frequency, and a computed risk level.

How the risk level is computed

Pick any state above for a full breakdown, or start from the most active states below. The risk level combines four signals from the USGS catalog — total catalogued M4+ count, the strongest magnitude ever recorded, the number of significant (M6+) events, and how consistently activity recurs year to year. States on active plate boundaries score Very High; interior states with sparse history score Low — though no state is earthquake-free.

Highest-activity states

The eight most seismically active U.S. jurisdictions by catalogued M4+ events. Select one for its full risk profile.

Alaska

8,804 M4+ events · strongest M7.9

Very High

Northern Mariana Islands

3,295 M4+ events · strongest M7.7

Very High

Guam

2,421 M4+ events · strongest M6.8

Very High

California

863 M4+ events · strongest M7.2

Very High

Puerto Rico

293 M4+ events · strongest M6.4

High

Oregon

260 M4+ events · strongest M6.3

High

U.S. Virgin Islands

212 M4+ events · strongest M6.1

High

Hawaii

198 M4+ events · strongest M6.9

High

Frequently Asked Questions

How is earthquake risk level determined? ▼
Risk levels (Low, Moderate, High, Very High) are determined by combining total earthquake count, maximum recorded magnitude, number of significant events (M6+), and the frequency of seismic activity across the 2005-2025 monitoring period.
What data does this calculator use? ▼
The calculator uses the USGS Comprehensive Earthquake Catalog (ComCat), covering earthquakes of magnitude 4.0 and above worldwide since 2005, over 310,000 events. US state figures are aggregated from that same global M4+ record.
Does low risk mean no earthquake danger? ▼
No. Low risk means fewer recorded events in the USGS dataset, but earthquakes can occur in any state. Areas with low historical activity can still experience damaging events. Always follow FEMA and USGS preparedness guidelines regardless of risk level.
What counts as a significant earthquake? ▼
For this calculator, significant earthquakes are those with magnitude 6.0 or greater. These events can cause substantial damage to buildings and infrastructure, especially in areas without seismic building codes.
How often is the data updated? ▼
The database covers USGS ComCat records from 2005 through 2025. Historical data is stable; new events are added periodically.

Data: USGS Comprehensive Earthquake Catalog (ComCat), magnitude 4.0+ worldwide since 2005. Risk levels are computed assessments and should not replace official USGS or FEMA hazard maps.