Earthquake Frequency: Is it on the Rise?

April 15, 2010; 10:00 AM ET
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This year has seen major quakes in Haiti, Chile, Mexico, and now China. However, while this succession of major, devastating quakes could be seen as unusual, there is little reason to believe that frequency of major earthquakes has increased significantly since the network of seismographs was established.

Photo by photos. com.

According to the United States Geological Survey, the annual number of earthquakes worldwide having a magnitude of M6.0-M6.9 is 134. For quakes M7.0-M7.9, the number lowers to 17. For great quakes of M8.0 or greater, the number is near 1.

The estimates for M6.0-M6.9 temblors are based upon data since 1990. Otherwise, the dates reflect observations since 1900.

Image Credit: USGS

For quakes above M7.0, there has been no important annual rise in frequency since 1900, according to the USGS. But reporting of quakes of M6.0-M6.9 seems to have risen perceptibly. That lesser earthquakes are reported with increasing frequency since the establishment of a seismic network likely owes to the continuing proliferation of seismic stations around the Earth.

Another important thing to consider is that the timing between natural events such as earthquakes tends to be uneven, with flurries of activity followed by relative breaks. This owes to the randomness that is inherent in natural phenomena.

Then, too, there is the matter of perception. A quick succession of major earthquakes can make headlines and become embedded in memory, but the spells of relative quiet are rarely, if ever, borne in mind.

Story by Senior Forecaster Jim Andrews.


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