Data Sources & Methodology
QuakeScan organizes publicly available earthquake event data from the USGS Earthquake Hazards Program (ANSS ComCat) into a searchable format. We normalize timestamps, coordinates, magnitudes, depth values, and location labels to make earthquake records easier to browse and understand.
Primary Data Source
All earthquake data on QuakeScan comes from the USGS Advanced National Seismic System (ANSS) Comprehensive Earthquake Catalog (ComCat). ComCat is the authoritative source for earthquake information in the United States and a primary aggregator of global seismic data from contributing networks worldwide.
The USGS makes this data freely available through their public API and web services. QuakeScan retrieves, normalizes, and indexes this data to make it browsable and searchable.
How Data Is Fetched and Processed
QuakeScan periodically queries the USGS ComCat API for new and updated earthquake events. Each event record is processed as follows:
- Timestamps are stored in UTC and converted for display
- Coordinates (latitude, longitude) are preserved at full precision
- Magnitudes are stored with their type (e.g., ml, mb, mw) and normalized for consistent display
- Depth values are stored in kilometers with classification labels (Shallow, Intermediate, Deep)
- Location descriptions are parsed to extract country, state/province, and tectonic region information
- PAGER alert levels, felt reports, and tsunami flags are preserved from the source data
Fields Included
| Field | Description |
|---|---|
| magnitude | Event magnitude (e.g., 5.2 mw) |
| depth_km | Depth of the hypocenter in kilometers |
| latitude / longitude | Epicenter coordinates |
| event_time | Date and time of the event (UTC) |
| place_description | Human-readable location (e.g., "25km NW of Tokyo, Japan") |
| felt_reports | Number of "Did You Feel It?" reports |
| alert_level | PAGER alert level (green, yellow, orange, red) |
| tsunami | Whether a tsunami warning was issued |
| significance | Calculated significance score (0-3000) |
Update Frequency
QuakeScan syncs with the USGS ComCat data on a regular schedule. New earthquake events typically appear on the site within minutes to hours of being reported by seismic networks. Historical data has been backfilled for significant events (M4.0+) dating back to the year 2000.
Known Limitations
- Magnitude revisions: Initial magnitude estimates are often revised as more seismic data is analyzed. QuakeScan updates records when the USGS revises them, but there may be a delay.
- Location accuracy: Epicenter locations are estimates based on seismic wave arrival times. Precision varies depending on network density and event depth.
- Detection thresholds: Very small earthquakes (below ~M2.0) are only reliably detected in areas with dense seismic networks. Coverage is less complete in remote or oceanic regions.
- Felt reports: "Did You Feel It?" data depends on voluntary public submissions and may not accurately represent the true impact of an event.
- Completeness: Our historical catalog may not include every event ever recorded by the USGS. We prioritize events M4.0+ for global coverage.
Important Disclaimer
QuakeScan is not a real-time alert or early warning system. Do not rely on this site for safety-critical decisions during seismic events. For official earthquake alerts and warnings, visit the USGS Earthquake Hazards Program or your local emergency management agency.