Tuesday, January 19, 2010

Missing Magnitude 4 Earthquakes

The statistics for earthquakes for the whole world in the last week give a rough impression of what is happening. There is a relative absence of earthquakes about magnitude 4.0. It seems to be indicative of two populations at the present time.

Another way of looking at the data is with a histogram which plots counts for equal intervals of magnitude. More data might give improved estimates of the probabilites of an earthquake of a given magnitude. That's one reason for studying all the earthquakes at this time. The accuracy of results depends on the number of events in a particular interval so one can't really trust the curve at higher magnitudes. There is no doubt that there are fewer 4.0s present.

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