Where every number comes from
Meridian never fabricates data. Each provider below is labelled with its class, licence and refresh cadence — and, where the feed service reports one, its current status. When a source is down or has no status, the platform says so instead of guessing.
| Provider | Domain | Licence | Refresh | Status |
|---|---|---|---|---|
USGS Earthquake Hazards US Geological Survey · OBSERVED | Earthquakes — Global, M ≥ 4.5 | Public domain (US Gov) | 5 min | ● UNAVAILABLE |
EMSC SeismicPortal Euro-Mediterranean Seismological Centre · OBSERVED | Earthquakes — Global, M ≥ 4 | Open, attribution required | 10 min (feed service) | ● UNAVAILABLE |
NASA EONET NASA Earth Science Data Systems · OBSERVED | Storms, fires, floods, volcanoes — Global, curated | Public domain (US Gov) | 15 min | ● UNAVAILABLE |
GDACS UN OCHA / European Commission JRC · OBSERVED | Earthquakes, cyclones, floods, volcanoes, fires, drought — Global, 6 hazard types | Open, attribution required | 10 min | ● UNAVAILABLE |
NASA FIRMS NASA LANCE · OBSERVED | Fire hotspots — Global, VIIRS/MODIS | Free MAP_KEY, attribution | ≤ 3 h | ● PLANNED |
Smithsonian Global Volcanism Program Smithsonian Institution · OBSERVED | Volcanic activity — Global | Non-commercial without permission | weekly | ● PLANNED |
PTWC / NTWC tsunami messages NOAA Tsunami Warning Centers · OFFICIAL WARNING | Tsunami messages — Pacific, Caribbean, Indian Ocean | Public domain (US Gov) | 5 min (feed service) | ● UNAVAILABLE |
IOC Sea Level Station Monitoring UNESCO IOC · OBSERVED | Sea level — 1,900+ stations | Non-commercial | 1 min | ● PLANNED |
WMO Severe Weather Information Centre World Meteorological Organization · OFFICIAL WARNING | National severe-weather warnings — 61 WMO members | Free, terms vary by WMO member — terms-review | 10 min (feed service) | ● UNAVAILABLE |
Meteoalarm EUMETNET · OFFICIAL WARNING | European weather warnings — 38 European services | Members-only production access | 10 min | ● PLANNED |
MET Norway alerts Norwegian Meteorological Institute · OFFICIAL WARNING | Norwegian weather warnings — Norway | CC BY 4.0 (attribution required) | 10 min | ● UNAVAILABLE |
Open-Meteo Open-Meteo.com · MODEL | Forecasts and place search (air quality, river discharge: PLANNED) — Global | CC BY 4.0 | on demand | ● LIVE |
NASA GIBS NASA Earth Science Data Systems · COMPOSITE | Daily satellite imagery (VIIRS true colour) — Global, daily polar-orbiter composite | Public domain (US Gov) | daily (VIIRS true colour, opt-in Live clouds) | ● UNAVAILABLE |
EUMETView EUMETSAT · COMPOSITE | Satellite imagery — Europe, Africa, Atlantic, Indian Ocean | EUMETSAT data policy — view services open | 10 min | ● PLANNED |
NOAA Climate Prediction Center NOAA · OBSERVED | ENSO indices (ONI, RONI) — Niño regions | Public domain (US Gov) | monthly | ● UNAVAILABLE |
NOAA OISST v2.1 NOAA NCEI / CoastWatch · OBSERVED | Sea-surface temperature (Niño 3.4) — Global oceans | Public domain (US Gov) | daily | ● UNAVAILABLE |
Open-Meteo Forecast Open-Meteo.com · MODEL | Conditions and 7-day forecast — global | CC BY 4.0 | on demand | ● LIVE |
Open-Meteo Geocoding Open-Meteo.com · place search | Place search — global | CC BY 4.0 | on demand | ● LIVE |
Status snapshot: unavailable · PLANNED = listed for licence review, not read yet · UNAVAILABLE = no current status from the feed service.
How Meridian scores
DERIVEDSeverity and fusion are computed by Meridian from the labelled sources above; place risk is specified and tested but not shown in the app yet. They are derived, not measured: they put different feeds on one scale and show their reasons, and they never claim a probability. The thresholds below are checked by automated tests against the code that scores events; rows and rules marked PLANNED are written but not yet shown in the app.
Severity
Each source reports severity in its own terms. Meridian maps them onto four levels: ▲ extreme, ◆ severe, ● moderate, ○ minor.
| Input | ▲ Extreme | ◆ Severe | ● Moderate | ○ Minor |
|---|---|---|---|---|
| Earthquake magnitude | M ≥ 7.0 | M ≥ 6.0 | M ≥ 5.3 | below |
| GDACS alert level + score | red | orange | green, score ≥ 1 | green, score below 1 |
| CAP severity (WMO SWIC, MET Norway) | Extreme | Severe | Moderate | Minor or Unknown |
| Flood return period (GloFAS) PLANNED — not yet shown in the app | ≥ 20 years | ≥ 5 years | ≥ 2 years | below 2 years |
| NASA EONET category (no intensity data) | — | storm, flood, volcano | wildfire, drought | other |
| Fire cluster, 24 h (NASA FIRMS) PLANNED — not yet shown in the app | ≥ 200 detections or FRP ≥ 1,000 MW | ≥ 50 detections | ≥ 10 detections | fewer |
| Volcano (Smithsonian GVP) PLANNED — not yet shown in the app | new eruption, VEI ≥ 3 | ongoing eruption, or new eruption below VEI 3 | unrest | — |
| Tsunami message (PTWC) | Warning | Advisory or Watch | Threat | Information |
Fusion
Records of the same category from different sources that match are fused into one event. A fused event holds at most one record per source, because a feed never reports one event twice: a main shock and its aftershock stay two events.
Earthquakes match when the epicentres are within 50 km, the magnitudes differ by at most 0.6 (when both sources give one) and the origin times are within 15 minutes. If either record has no origin time, their last-update times are compared instead.
Every other category matches when the centres are within 150 km and there is a gap of at most 24 hours between the periods the two were active (first report to last update).
A fused event keeps the highest severity, lists every source, and is led by the highest-ranked source: GDACS, USGS, EMSC, PTWC, GVP, FIRMS, NASA EONET. National warnings (WMO SWIC, MET Norway) are never fused with events; they are kept as their own layer.
Place risk
PLANNED — not yet shown in the appFor each saved place the risk is the largest of (severity weight × distance decay) over events within 300 km. Weights: extreme 1.0, severe 0.75, moderate 0.5, minor 0.25. The decay falls in a straight line from 1 at the place to 0 at 300 km. Events known only to country level are ignored.
An official warning that applies to the place sets a floor: its polygon contains the place, or its district or point is within 50 km. Extreme sets at least Severe, Severe at least High, Moderate at least Moderate; Minor sets none. Country-level warnings never apply to a place.
A river discharge return period of 20 years or more sets at least High, 5 years or more at least Moderate. PM2.5 above 55 µg/m³ sets at least Moderate.
Levels: Low below 0.25, Moderate from 0.25, High from 0.5, Severe from 0.75. The result is the level plus the ordered list of reasons behind it.
It is derived by Meridian from events and official warnings: not a probability, a forecast or an official assessment.
Badges. OBSERVED = a measurement that happened. OFFICIAL WARNING = issued by the named authority: national weather warnings are drawn as hollow shapes, never as observed events; NOAA tsunami messages carry the badge and their message type (an information statement says there is no tsunami threat) in every list and detail. MODEL / FORECAST = a model estimate with uncertainty. COMPOSITE = satellite imagery assembled from several sources. DERIVED = computed by Meridian from other labelled data. HISTORICAL = archived observations. STALE / UNREACHABLE = the last good data is at least 15 / 60 minutes old. DEMO and EDUCATIONAL = sample values or illustration, clearly flagged, never a measurement.
Failure policy. If a feed is unreachable, its panels say so. Nothing is interpolated, simulated or quietly reused past its freshness window.
Data: USGS · EMSC · NASA EONET · GDACS · NOAA PTWC/NTWC · WMO SWIC · MET Norway (CC BY 4.0) · Open-Meteo (CC BY 4.0) · NASA GIBS · NOAA CPC · NOAA OISST · land geometry © Natural Earth via world-atlas. Sources marked PLANNED are listed for licence review and are not read yet, so they are not credited here.