Methodology & Data Sources

Primary Data Source

All seismic data comes from the US Geological Survey (USGS) Earthquake Hazards Program via the USGS ComCat (Comprehensive Earthquake Catalog) API. USGS ComCat is the authoritative global earthquake catalog, integrating seismic network data from around the world.

We use two catalog segments:

• Global M4+ Catalog (2005-2025): All earthquakes of magnitude 4.0 and above recorded worldwide. Over 300,000 events.
• Significant Earthquake Catalog (1900-present): Major earthquakes of magnitude 6.0 or greater with historical data. Approximately 14,000 events.

Processing Pipeline

We query the USGS ComCat API and download the full earthquake catalog for our coverage period. Each earthquake record is processed through our ETL pipeline:

• Each event is geocoded to a country using USGS place descriptions and coordinate-to-country mapping based on geographic boundary datasets
• US events are additionally mapped to states using coordinate-to-state boundary matching for state-level seismic profiles
• Magnitude distribution histograms are computed (M4-4.9, M5-5.9, M6-6.9, M7-7.9, M8+) per country, state, and year to show the frequency of events at each magnitude level
• Annual totals, maximum magnitudes, and significant event counts are aggregated per geographic unit to enable year-over-year trend analysis
• Depth statistics (shallow less than 70km, intermediate 70-300km, deep greater than 300km) are computed from reported focal depths to characterize the tectonic setting of each region

USGS-reported parameters, magnitude, depth, time, location, are presented without modification. No seismic data is interpolated, estimated, or editorially adjusted.

Magnitude Scale

USGS reports magnitudes using the most appropriate scale for each event, typically moment magnitude (Mw) for significant events and local magnitude (ML) or duration magnitude (Md) for smaller events. The Mw scale is the modern standard and is logarithmic: each whole number increase represents approximately 31.6× more energy released. An M7 earthquake releases roughly 1,000 times more energy than an M5.

Data Collection Method

USGS ComCat aggregates seismic data from a global network of seismograph stations operated by USGS, regional seismic networks, and international partner agencies. When an earthquake occurs, seismic waves are detected by multiple stations, and automated algorithms determine the event's location, depth, and magnitude. These parameters are refined by seismologists and published to the ComCat database, typically within minutes for significant events. Our pipeline queries the ComCat API to download the full catalog for our coverage period and processes each event record individually.

Update Schedule

The USGS ComCat catalog is updated continuously as new earthquakes are detected and as existing event parameters are refined. We refresh our database periodically to capture new events and magnitude revisions. Recent earthquakes (within the past 30 days) may not yet appear in our database if they occurred after our most recent data refresh. For real-time earthquake information, always refer directly to the USGS Earthquake Hazards Program website.

Limitations

• Detection completeness varies by region. Remote oceanic areas and regions with sparse seismic networks may have incomplete records for M4-5 earthquakes.
• Historical data (pre-1960) has larger magnitude uncertainties than modern instrumental data. Early magnitude estimates can differ by ±0.3-0.5 from modern recalculations.
• Country attribution uses USGS place names and coordinate mapping, which may not perfectly match political boundaries in border regions.
• USGS catalogs are retroactively revised, magnitudes for recent events may be updated after initial posting.
• Depth statistics are reported as determined by USGS; shallow events (less than 70 km) can have depth uncertainties of several kilometers, especially in areas with sparse station coverage.
• Do not use PlainQuake as a substitute for official earthquake warnings or emergency information.

Not Affiliated

PlainQuake is not affiliated with the USGS, any seismic network, or any government agency. This site is for informational and educational purposes only.