Why Two Agencies Report the Same Disaster Differently — and Which Number to Trust

WND Editorial Team Published: Aug 13, 2026 Updated: Aug 23, 2026 6 min read

Direct answer: most disagreements come from four causes, and none of them is error. The first number is automatic and gets revised within hours. Different agencies use different scales that legitimately produce different values for the same event. They use different instrument networks at different distances. And they answer different questions — a satellite measures where something is burning, a government measures what was destroyed. When two figures conflict, prefer the agency responsible for that territory, prefer a reviewed figure over an automatic one, and prefer the most recent.

The first number you see is a machine's first guess

Within a minute or two of a large earthquake, an automatic system has already published a magnitude, a location and a depth. Nobody has looked at it. It was computed from whichever stations had reported by then, which for a very recent event is a small and geographically lopsided sample.

Over the following minutes and hours more stations report, an analyst reviews the solution, and the numbers move. This is normal and the agencies say so plainly: early values are explicitly provisional. It is also why two sites can show different magnitudes for the same event at the same moment — one is showing an automatic solution and the other a revised one, or both are automatic and were computed seconds apart.

If you are reading a magnitude in the first hour, you are reading a draft. That is not a criticism of the system; speed is the point, and a warning that waited for certainty would be useless.

Different scales, all of them correct

“Magnitude” is not one measurement. It is a family of them, and they do not return the same value for the same earthquake.

Local magnitude (ML) is the original Richter-style measurement, based on the amplitude recorded on nearby instruments. It works well for moderate, nearby earthquakes.
Body-wave (mb) and surface-wave (Ms) magnitudes are computed from different parts of the seismic wavetrain, and each is suited to a different range of size and distance.
Moment magnitude (Mw) is derived from the physical size of the rupture — how much rock moved, how far, over what area. It is the modern standard for significant earthquakes.

The older scales share a limitation: for the very largest earthquakes they stop rising meaningfully, because the instruments and wave periods they rely on are already at their limits. Two enormous earthquakes of clearly different size can return nearly the same number on those scales. Moment magnitude does not have that ceiling, which is precisely why it became standard.

So an agency reporting mb and an agency reporting Mw for the same event are not contradicting each other. They are answering slightly different questions and often do not say which one on the headline figure. If a report does not name the scale, it is telling you less than it appears to.

Different networks see a different earthquake

An agency computes from the instruments it has. A national network sitting directly above the rupture has dense, close coverage; a global network computing the same event from thousands of kilometres away has excellent distant coverage and poor local detail. Both produce a legitimate answer, and the answers differ.

This matters most for the numbers that are not the magnitude. Depth is the hardest quantity to resolve remotely and often moves the most between revisions — and depth, far more than magnitude, decides whether a given earthquake is felt as a rattle or as a disaster. Epicentre location can shift by tens of kilometres between an early and a final solution, which is enough to change which town is described as nearest.

It is not only earthquakes

Wildfire area. A satellite product reports thermal detections on a grid — where heat is visible from orbit, cloud permitting. A ground agency reports a mapped perimeter after survey. The satellite figure appears within hours and is approximate by construction; the surveyed figure appears later and is the one that ends up in the record.
Cyclone intensity. Agencies do not all average wind over the same period. Some quote a one-minute sustained wind, others a ten-minute sustained wind. Averaging the same gusty wind over a longer period always yields the lower number, so the same storm is legitimately reported as stronger by one centre than another — before anyone disagrees about anything physical.
Flood extent. Satellite-mapped water area, modelled inundation and officially declared affected districts are three different quantities, and they are frequently reported as though they were one.
Casualties. Confirmed, reported and estimated deaths are different counts produced by different processes, which is a large enough subject to have its own article.

Which number to trust

Prefer the agency responsible for that territory. For an event inside a country's own monitoring area, its national agency usually has the densest instrument coverage and the clearest mandate. Each of our country pages links that country's official agencies.
Prefer reviewed over automatic. If a figure is still marked provisional, preliminary or automatic, treat it as one.
Prefer the most recent. Revisions move towards the truth. An old number that is still circulating is not a second opinion.
Check that the units are the same question. Before concluding two sources disagree, check the magnitude scale, the wind averaging period, or whether “affected” means mapped, modelled or declared.
Do not average them. A number halfway between two measurements of different things is a measurement of nothing.

For deciding what to do, the disputed number is usually the wrong one

Arguments about whether an earthquake was 6.2 or 6.4 rarely change any decision. What determines harm is depth, distance from the rupture, the ground underneath, and what the buildings are made of — and a difference of a few tenths of magnitude is small beside any of them. The same is true elsewhere: a cyclone's category does not tell you whether your area floods, which is a question about storm surge and elevation.

Precision in the headline figure is worth much less than knowing which agency has authority where you are, and what they are currently telling you to do.

What this site does with the disagreement

We aggregate several of these feeds at once, so we meet this every day, and our policy is deliberately conservative:

We never average or reconcile conflicting figures. Each event keeps the numbers its source published.
We always name the originating agency and link its original record, so any figure quoted here can be checked at its source — and so it is clear whose measurement it is.
Where more than one agency has reported the same event, we keep the additional reports alongside rather than discarding them.
We are not an authority on any of these numbers. We are a place where they can be seen together. When we and an agency differ, the agency is right.

How events are matched and what is kept is set out in our methodology, and the feeds themselves are listed under data sources.

This article explains why published figures differ in general. This site is not a measuring authority and does not produce its own magnitudes, areas or casualty counts; for the authoritative figure, use the agency named on the event.

Frequently asked questions

Why does USGS say one magnitude and another agency say a different one?

Usually one of three reasons. The figure may be an automatic solution that has not yet been reviewed, and early values are explicitly provisional. The two agencies may be quoting different magnitude scales — moment magnitude, body-wave magnitude and local magnitude legitimately return different values for the same earthquake. Or they computed from different instrument networks at different distances from the rupture. None of these is an error, and the difference is usually a few tenths.

Which magnitude scale is the right one?

Moment magnitude (Mw) is the modern standard for significant earthquakes, because it is derived from the physical size of the rupture and does not stop rising for very large events the way older scales do. For small, local earthquakes the older local magnitude is still perfectly adequate. The important thing is to compare like with like: two numbers on different scales are not in conflict.

Why do earthquake magnitudes change hours after the event?

Because the first value is computed automatically from whatever stations had reported within a minute or two, and more data arrives continuously afterwards. An analyst then reviews the solution. Revisions move the number towards the truth, so the most recent figure is the one to use — and the location and especially the depth often move more than the magnitude does.

Why do two agencies report different wind speeds for the same cyclone?

Because they do not average the wind over the same period. Some centres quote a one-minute sustained wind and others a ten-minute sustained wind. Averaging the same gusty wind over a longer period always produces a lower number, so the same storm can be reported at different intensities without anyone disagreeing about the storm itself. Check the averaging period before concluding the sources conflict.

Why is the burned area of a wildfire reported differently?

A satellite product reports heat detections on a grid, available within hours and approximate by construction, and limited by cloud cover. A ground agency reports a mapped perimeter after survey, which takes longer and is what ends up in the official record. They are measuring different things at different times, so the two figures are not directly comparable.

If sources disagree, should I average them?

No. The figures usually come from different scales, different instruments or different definitions, so a value halfway between them corresponds to nothing that was measured. Take the figure from the agency with authority over that territory, prefer a reviewed value over an automatic one, and prefer the most recent.

Does a difference of a few tenths of magnitude matter?

Rarely for any decision you would make. Harm is determined much more by depth, distance from the rupture, local ground conditions and building construction than by a small difference in the headline magnitude. What matters is which agency has authority where you are and what they are currently advising.

Sources

About the author

WND Editorial Team — The World Natural Disasters editorial team curates disaster information from official scientific and humanitarian sources, reviews safety guidance against public-agency recommendations, and maintains the historical database.

Written and reviewed under our editorial policy. Factual claims cite the sources listed above.

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