PlainQuake

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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.

This tool, in one line

4 of 39 tracked U.S. states and territories carry a computed "Very High" risk level -- pick any state above for its full breakdown.

39
states & territories tracked
4
rated "Very High" risk

According to the U.S. Geological Survey's Earthquake Hazards Program, as of 2026-08-26 the ComCat catalog this calculator draws from records 317,293 magnitude-4+ earthquakes worldwide since 2005, every state's risk level computed from that same dataset using the methodology described on our methodology page.

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. This is a historical-activity read, not a predictive hazard model; actual risk to a specific structure also depends on local building codes, soil type, and construction quality, not seismic history alone.

Highest-activity states

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

M4+ events by state, the 8 most active

Catalogued magnitude-4-and-above earthquakes, USGS ComCat since 2005

M4+ events
Source USGS Comprehensive Earthquake Catalog (ComCat) As of 2005–present

Alaska

8,996 M4+ events · strongest M8.2

Very High

Northern Mariana Islands

3,345 M4+ events · strongest M7.7

Very High

Guam

2,465 M4+ events · strongest M6.8

Very High

California

885 M4+ events · strongest M7.2

Very High

Puerto Rico

297 M4+ events · strongest M6.4

High

Oregon

267 M4+ events · strongest M6.3

High

U.S. Virgin Islands

222 M4+ events · strongest M6.1

High

Hawaii

206 M4+ events · strongest M6.9

High

What to do with your risk level

Alaska tops the leaderboard at "Very High" risk, 8,996 M4+ events on record, but every state has SOME computed risk level.

  • Select any of the 39 tracked states above to see its own event count, strongest recorded magnitude, and yearly trend. Browse all states
  • Risk level is computed from three signals (total events, strongest magnitude, significant-event count) - see exactly how a level is assigned. Read the methodology

Risk levels are relative rankings within this dataset (USGS M4+ catalog, 2005–present), not an official USGS or FEMA hazard designation.

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 complete-year monitoring window.
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.

According to the US Geological Survey Earthquake Hazards Program, PlainQuake's figures are rendered directly from 317,293 recorded M4+ earthquakes and 14,444 significant M6+ events (USGS ComCat, 2005-present) -- no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2026-08-26.