Earthquake Guides
Educational resources to help you understand seismic data, earthquake measurement, and regional risk patterns. Data from the USGS Comprehensive Earthquake Catalog (ComCat); see our methodology.
All guides reference USGS ComCat earthquake data covering 310,000+ M4.0+ events worldwide from 2005 onward, plus significant M6.0+ events back to 1900.
How Earthquakes Are Measured
Moment magnitude, seismograph networks, depth classification, and how USGS detects and locates earthquakes worldwide.
Earthquake Risk in the US
Which US regions face the most seismic risk, major fault lines, historical patterns, and what USGS data reveals about frequency.
Reading Earthquake Data
How to interpret PlainQuake data: magnitude, depth, location, what makes an earthquake dangerous, and yearly statistics.
Earthquake Preparedness Guide
Practical preparedness: emergency supplies checklist, household plan, building safety, and what to do during and after an earthquake.
Most Seismically Active Regions in the US
US states ranked by earthquake frequency and magnitude. Top seismic zones, major fault lines, and regional earthquake patterns from USGS data.
Earthquake Magnitude Scales Explained
The Richter scale, moment magnitude, body wave magnitude, and surface wave magnitude, how each works, why they differ, and which one USGS actually uses.
Understanding Seismic Risk Maps
How to read USGS seismic hazard maps: what the colors mean, how probabilities work, and how hazard maps shape building codes across America.
Methodology
Our guides explain the single dataset behind this site: the USGS Comprehensive Earthquake Catalog (ComCat). All counts, magnitudes, and figures shown across PlainQuake are computed automatically from that catalog, with the source referenced throughout.
We aim to present seismic data in plain language that is accessible to general audiences. Where magnitude scales, detection thresholds, or catalog revisions affect interpretation, we note these inline. The figures are derived directly from the USGS source, see our methodology for the full pipeline and corrections process.