Time for another pet peeve (in addition to the narrative description of evolution). The use of the Richter Scale. Now, the USGS changed its policy back in January 2002, and has not reported earthquakes using Richter magnitude since then. Rather, it uses the moment magnitude.
The moment magnitude, up to a point, is identical to the Richter magnitude. However, with large earthquakes, anything above magnitude 6.0 (on either scale), the two measurements start to diverge. The Richter scale saturates, which is to say that proportionately much larger earthquakes have lower numbers than would be expected on a strict logarithmic scale. So while a magnitude 5.0 earthquake is approximately 32 times stronger than a magnitude 4.0 earthquake, a magnitude 8.0 earthquake may actually be 1000 times stronger than a magnitude 7.0, but the Richter scale won't tell you this.
Far better to use the moment magnitude (although the USGS apparently does not use it for earthquakes below 3.5 - but then such small earthquakes are only ever publicised locally), which for every unit indicates an increase in strength of 101.5, or about 36.1 times, throughout the scale. I wish I could find the graph that illustrated this point beautifully - perhaps Highly Allochthonous can oblige (as I'm straying dangerously into subjects that I understand but not enough to convey my point succinctly).
So my point anyway. The USGS uses the moment magnitude to report all earthquakes over magnitude 3.5. We don't hear about international earthquakes below about magnitude 5.0. So if our news reporters are relying on USGS earthquake alerts (which is likely), the figures they are giving out are moment magnitude figures and not Richter magnitude figures. This morning an earthquake in the Atlantic, off the coast of Brazil, was reported. There is very little news online - the most I have been able to get is a short briefing: Quake rocks Atlantic Ocean, north of Brazilian coast.
Yet this morning on the radio, a BBC reporter happily told us that this earthquake measured 6.6 "on the Richter scale". Now, it may well be that a moment magnitude of 6.6 is almost identical to a Richter magnitude of 6.6, but that was not what was measured, nor was it what was reported. It's like this - imagine reporting temperatures, that are reported on the Celsius scale, on the Fahrenheit scale. At a certain temperature, -40°, the numerical values of the temperature in Celsius and Fahrenheit are the same. So you can get away with it. But you can't report 32°Fahrenheit as 32 degrees Celsius. You can't report 100°Celsius as 100°Fahrenheit. You would be misleading the public (and possibly quite dangerously, if you're giving the weather forecast).
And reporting a seismic moment magnitude as being on the Richter scale is similarly misleading the public. Yes, there is a semi-argument for the general public not knowing anything other than the Richter scale, for it being retained as a sort of allegory - "It's not really on the Richter scale, but you the general public are incapable of understanding moment magnitude". But isn't that a bit insulting? Aren't you all intelligent enough to deal with an earthquake that's "magnitude 6.6" without having a redundant and inaccurate "on the Richter scale" tagged on the end?
The moment magnitude, up to a point, is identical to the Richter magnitude. However, with large earthquakes, anything above magnitude 6.0 (on either scale), the two measurements start to diverge. The Richter scale saturates, which is to say that proportionately much larger earthquakes have lower numbers than would be expected on a strict logarithmic scale. So while a magnitude 5.0 earthquake is approximately 32 times stronger than a magnitude 4.0 earthquake, a magnitude 8.0 earthquake may actually be 1000 times stronger than a magnitude 7.0, but the Richter scale won't tell you this.
Far better to use the moment magnitude (although the USGS apparently does not use it for earthquakes below 3.5 - but then such small earthquakes are only ever publicised locally), which for every unit indicates an increase in strength of 101.5, or about 36.1 times, throughout the scale. I wish I could find the graph that illustrated this point beautifully - perhaps Highly Allochthonous can oblige (as I'm straying dangerously into subjects that I understand but not enough to convey my point succinctly).
So my point anyway. The USGS uses the moment magnitude to report all earthquakes over magnitude 3.5. We don't hear about international earthquakes below about magnitude 5.0. So if our news reporters are relying on USGS earthquake alerts (which is likely), the figures they are giving out are moment magnitude figures and not Richter magnitude figures. This morning an earthquake in the Atlantic, off the coast of Brazil, was reported. There is very little news online - the most I have been able to get is a short briefing: Quake rocks Atlantic Ocean, north of Brazilian coast.
Yet this morning on the radio, a BBC reporter happily told us that this earthquake measured 6.6 "on the Richter scale". Now, it may well be that a moment magnitude of 6.6 is almost identical to a Richter magnitude of 6.6, but that was not what was measured, nor was it what was reported. It's like this - imagine reporting temperatures, that are reported on the Celsius scale, on the Fahrenheit scale. At a certain temperature, -40°, the numerical values of the temperature in Celsius and Fahrenheit are the same. So you can get away with it. But you can't report 32°Fahrenheit as 32 degrees Celsius. You can't report 100°Celsius as 100°Fahrenheit. You would be misleading the public (and possibly quite dangerously, if you're giving the weather forecast).
And reporting a seismic moment magnitude as being on the Richter scale is similarly misleading the public. Yes, there is a semi-argument for the general public not knowing anything other than the Richter scale, for it being retained as a sort of allegory - "It's not really on the Richter scale, but you the general public are incapable of understanding moment magnitude". But isn't that a bit insulting? Aren't you all intelligent enough to deal with an earthquake that's "magnitude 6.6" without having a redundant and inaccurate "on the Richter scale" tagged on the end?
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