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The importance of explaining your chart: the case of the red 118

Still shaken from the quake

On the news that the tsunami warning has been called off in Asia, I reminded myself of the human toll of the 2004 calamity by looking up Wikipedia (link).

I didn't receive a warm greeting as I was confronted with the following pie chart:



Maybe someone can help me understand what is being plotted here.

Maybe the designer was still shaken from the devastation of the quake when this was drawn?


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The graph shows the proportion of the total global seismic moment release between 1906 and 2005 (1.0 x 10^24 Newton-meters) by moment magnitude non-equal bins. The four with specific event names are single event bins. I think the author was trying to relate event moment magnitudes with seismic moment share. The labels make the graph confusing because they are not related to the number that is being graphed, other than acting as bin labels.

At least that is the best I can make of it with help from Wikipedia,


For the four single events or the four bins, you could calculate their seismic moment from their moment magnitudes. So for the 2004 Sumatran event with a moment magnitude rating of 9.3, the seismic moment (or energy released) was 1.12x10^23 or 11% of all energy released by all events between 1906 and 2005 which looks to be be equal to the energy released by all events with a moment magnitude rating of 7 or below.

The ordering is confusing because it is partially ordered clockwise by moment magnitude bin value. Also, the "Other" slice should be labeled "9.3>M>=8".

Thomas Schwenn

The file is hosted here

Anyone with a Wikimedia/Wikipedia account can submit a replacement with the "Upload a new version of this file" link on that page.

It should be remade as a bar chart, right? And that title is misleading: the range of dates implies that the chart portrays all seismic events from 1906 through 2005, but there is no "other events" pie slice.

Gregory Shrock

The chart illustrates that the Richter scale is an exponential function and not a linear one. That is to say that an earthquake of 9.0 on the Richter scale is many times the size of an earthquake of 8.0.

It shows all of the seismic energy released by all earthquakes from January 1906 to December 2005. The 1960 Chile earthquake (9.5 on the Richter scale) released - all by itself - about 1/5 of all of the energy released by all of the century's earthquakes. The 9.4 Alaska earthquake about 1/6; and the 9.3 Sumatra earthquake about 1/8. Those three earthquakes alone accounted for almost half of all the energy released.

By contrast, there were thousands of earthquakes below 6.0 (the slice labeled Mw < 6.0), but collectively they released less than half of the energy that the Sumatra earthquake alone did.

Similarly with the slices for earthquakes greater than 6.0 but less than 7.0, greater than 7.0 and less and 8.0 and greater than 8.0 but less than 9.0.

The tiny slice labeled San Francisco (1906) shows how small the San Francisco earthquake was compared to the big three above 9.0.

dan l

The chart illustrates that the Richter scale is an exponential function and not a linear one.

That may very well be what the data illustrates. Definitely not what the chart says....

Gaithersburg Borstal Boy

According to Wikipedia the Newton Meter can be used as a unit of energy, like the joule. The pie chart is showing the amount of energy released in the 7 largest earthquakes in the last 100 years.

Gaithersburg Borstal Boy

This was a chart for techies by techies.

Sarah Gerweck

I have to laugh at the "the Newton-meter [is] like the Joule"—given that definition of a Joule is the Newton-meter.

Others have explained the graph, but none simply. In simple terms, the whole pie is all the energy released in all earthquakes from the last 106 years. Some of the famous earthquakes are called out for reference.

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