How Earthquake Monitoring and USGS Data Work
Understand seismic networks, automatic detections, analyst review, USGS GeoJSON feeds, event updates, significance, and catalog limitations.
A live earthquake tracker is the visible end of a much larger observing system. Instruments measure ground motion, networks transmit waveforms, computers identify possible events, analysts review important solutions, and data services publish a catalog that can evolve from a rapid preliminary record into a refined historical entry.
EarthQuakeTracker uses official USGS earthquake feeds as its primary source. Understanding that source chain explains why data can update, why some fields are empty, and why small-event coverage differs across regions. This guide documents the process and our presentation methodology without claiming to be an official monitoring agency.
Seismic networks observe ground motion
A seismic station contains sensors that record motion over a range of frequencies. Networks position stations across a region, transmit waveforms to processing centers, and maintain timing and calibration so records can be compared. Strong earthquakes can be detected globally, while the completeness of small-event catalogs depends heavily on nearby station density and noise conditions.
The USGS Earthquake Hazards Program works with regional, national, and international partners. A published event can therefore contain contributions from more than one network or agency, and its preferred solution may change as those observations are reviewed.
Automatic systems detect and associate arrivals
Continuous waveforms contain earthquakes, environmental noise, cultural noise, and instrument signals. Detection software identifies candidate arrivals and associates phases from multiple stations that could share one source. It then estimates origin time, location, depth, and magnitude. Rapid automatic processing is essential for timely information, especially immediately after felt events.
Automation can also produce imperfect early solutions. Nearby events may overlap, a noisy signal may be misidentified, or limited station geometry may constrain depth poorly. Networks use thresholds, quality measures, and later review to reduce errors. Small events may remain automatic, while significant events receive more intensive analysis.
Human review and additional data refine the catalog
Analysts inspect waveforms, adjust phase picks, add or remove stations, compare magnitude types, and review event classification. Some waves needed for robust large-earthquake calculations take time to reach distant stations, and not every contributing waveform arrives in real time. The preferred magnitude and location can therefore change in the hours or days after an event.
Historical catalogs can also be revised when better methods or newly recovered data become available. A catalog is not a static newspaper archive; it is a scientific dataset. Users should record when they accessed preliminary information and retrieve the current official solution when accuracy matters.
What the USGS GeoJSON feed contains
GeoJSON represents each earthquake as a feature with geographic coordinates and descriptive properties. Summary feeds include identifiers, magnitude, place, time, update time, alert and felt fields when available, significance, status, event type, and links. Geometry coordinates are ordered longitude, latitude, and depth—a detail developers must handle correctly.
USGS publishes feeds for common time windows and magnitude thresholds. These feeds are designed for applications and update frequently, but a feed is still a catalog snapshot. An event-detail product contains more information than the summary record, including related scientific products when available.
How EarthQuakeTracker handles the source
Our browser normally requests a specific EarthQuakeTracker server endpoint. The server permits only trusted USGS feed choices, applies a timeout, validates the response shape, normalizes fields, and returns a limited event set. The interface exposes loading, retry, empty, and source-unavailable states instead of substituting fake earthquake data.
Map circles and summary statistics are derived from the returned events. The strongest value is the largest current magnitude in the selected set; average depth is calculated from those real records; event counts change with the time and magnitude filters. Every list item links to the USGS source page for verification.
Significance, alerts, and responsible limits
The USGS significance value uses more than magnitude. Its published method also considers Did You Feel It responses and PAGER alert level. A significant-event list is therefore an impact-aware selection, not merely a list sorted from strongest to weakest. Fields may remain empty when the relevant product does not exist.
EarthQuakeTracker does not issue earthquake early warning, prediction, evacuation orders, or structural assessments. An early-warning message is an official notification sent after an earthquake has started but before strong shaking reaches some locations; a recent-event webpage is not equivalent. Use national and local official channels for alerts and safety decisions.
Questions About This Topic
Is EarthQuakeTracker part of the USGS?
No. It is an independent presentation layer that uses public USGS data.
How often do USGS feeds update?
The official summary-feed documentation states that common past-hour, past-day, and past-seven-day feeds update every minute. Individual records can still change on a different review schedule.
Why is a field marked unavailable?
Some products, such as felt reports or alert levels, do not exist for every event. The tracker omits or labels missing data rather than inventing a value.
Can I use the feed for research?
Use the official USGS catalog or web services for research, document your query and access time, and review completeness and uncertainty for the intended analysis.