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Why Weather Sites Showed Earthquakes

Weather sites showed USGS earthquakes because visitors asked; seismic and meteorological observations use different instruments and agencies.

Back to Historical weather observations and forecasts

Personal weather sites added earthquake lists because visitors treated “what’s happening” as one page, not because a rain gauge detects seismic waves. The usual source was a U.S. Geological Survey (USGS) catalog feed. That feed is a seismic observation product from contributing networks. It is not a meteorological observation, and a weather site that displays it is not a seismic network. TNET Weather is not a warning service for earthquakes or for weather. For events and aftershocks, use USGS Latest Earthquakes. For weather hazards, use weather.gov.

This article is the why and the citation rule. How a Cumulus PHP site should embed a USGS list without flooding visitors is a different host and a different angle: cumulus.tnetweather.com/earthquake.

Historical context

/earthquake on tnetweather.com is a continuity stub for a backlink that named the subject, not a recovered interactive map. Early-2000s PWS templates often reserved a sidebar for “recent earthquakes” next to current temperature, because the same audience that watched monsoon storms also felt or read about regional quakes and expected the weather page to mention them. The original include, map, and any then-current event list are not rehosted. This URL does not display earthquakes.

The scientific reason to keep the URL is the evidence split the old sidebar usually blurred.

Seismic versus meteorological observations

A weather station observes the atmosphere and the land–air interface: temperature, humidity, pressure, wind, precipitation, and sometimes lightning or radiation. Its instruments are thermometers, hygrometers, barometers, anemometers, collectors, and optical or radio lightning sensors. In the United States the official warning authority for hazardous weather is the National Weather Service.

An earthquake observation is a seismic event: origin time, hypocenter (latitude, longitude, depth), and magnitude, produced by seismometers and processed by seismic networks. In the United States the catalog that weather sites actually republished is the ANSS Comprehensive Earthquake Catalog (ComCat), assembled by USGS from contributing networks (ComCat documentation; last checked 13 August 2026). USGS is not NWS. A seismograph is not a barometer. A magnitude is not a wind gust.

Felt shaking can coincide with weather (people notice both; storms can trigger small landslide noise that is not a tectonic earthquake). Coincidence is not a shared instrument. Do not treat a pressure spike as a quake, and do not treat an M3 catalog entry as a thunderstorm.

Agencies stay separate in the caption:

| Family | Typical instrument | U.S. catalog / warning home | |---|---|---| | Meteorological | PWS or ASOS/AWOS sensors | NWS / weather.gov | | Seismic | Seismometers in contributing networks | USGS ComCat / earthquake.usgs.gov |

A PWS that shows both is a republisher of the USGS family, not a member of ANSS.

What the USGS record actually contains

ComCat event pages and the GeoJSON summary feed carry fields a weather site can cite without pretending to locate the event itself (GeoJSON summary format; ComCat data dictionary):

  • Origin time (time). The time rupture initiates, in UTC (milliseconds since 1970-01-01T00:00:00.000Z in the feed; readable UTC on the event page). Large earthquakes can continue rupturing for tens of seconds. Origin time is not “when I felt it” and not the feed’s updated stamp.
  • Magnitude (mag) and magnitude type (magType). Magnitude is a number with a type (for example Ml, Mw, mb). Types are not interchangeable at the precision a sidebar implies. Dropping magType and printing “M4.2” as if all magnitudes were one scale is a citation error.
  • Location. Geometry is longitude, latitude, and depth (hypocenter). The place string (“14 km SSW of…”) is a human label, not a surveyed street address. Prefer coordinates plus depth for any archive; keep place as the public gloss.
  • Event type and status. ComCat includes earthquakes and other seismic events (for example quarry blasts). status distinguishes automatic locations from reviewed ones. An automatic M2.1 can move or disappear after review.
  • Event page URL. The durable citation is the USGS event page (url in GeoJSON), not a screenshot of a PWS sidebar.

The feed also carries generated in metadata: when that summary file was built. That is not origin time. A weather page that prints only “Updated just now” is labeling the poll, not the earthquake.

How to cite an event on a weather site

Write a one-line citation that a later reader can check:

USGS ComCat: origin 2024-07-13 18:20:11 UTC, M4.2 (ml), 33.41°N 116.44°W, depth 11 km, “14 km SSW of…”. Automatic/reviewed as stated on the event page. Source: [USGS event URL]. This weather site is not a seismic network.

Rules that follow from the fields:

  1. Always include origin time in UTC. If you also show local time, label the zone. Arizona’s MST-versus-PDT split is a weather-page problem; do not silently convert USGS UTC to “station time.”
  2. Always include magnitude type, or link the event page where type is shown.
  3. Do not upgrade place to a city-level warning. Felt reports (DYFI) and PAGER alert colors, when present, are USGS products—not NWS watches and not TNET alerts.
  4. Say whether the row is automatic or reviewed if the feed provides status.
  5. Link USGS. Do not host a parallel “TNET earthquake warning.”

If the historical sidebar had no magnitude filter, do not invent one in hindsight. Describe the principle; the Cumulus-host article is where feed filters belong as an implementation problem.

Not a seismic network

Republishing ComCat does not enroll the PWS in ANSS. The station has no claimed detection efficiency, no phase picks, and no authority to issue aftershock forecasts. Dropping events that “don’t look local,” coloring rows like weather warnings, or mixing quake rows into the same “alerts” module as NWS headlines is how a hobby page impersonates two agencies at once.

USGS products are not a substitute for local emergency instructions after a felt earthquake. Gas, structural, and tsunami questions belong to local authorities and, where relevant, tsunami warning centers—not to a weather template.

Modern relevance

TNET’s connection research groups atmospheric observations as one evidence family among others. An earthquake catalog is a different family and a different agency. Keeping that split visible is the same discipline as not treating a model field as a station reading. See how the service works for observed versus modelled versus derived information, and evidence families for how TNET talks about atmospheric inputs. Neither page is a seismic feed.

Related weather-side observation pages: NWS products on a PWS, lightning as a local observation. Hub: historical observations.

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