This year has seen major quakes in Haiti, Chile, Mexico, and now China.However, while this succession of major, devastating quakes could be seen asunusual, there is little reason to believe that frequency of major earthquakeshas increased significantly since the network of seismographs was established.
Image Credit: USGS
According to the United States Geological Survey, the annual number ofearthquakes worldwide having a magnitude of M6.0-M6.9 is 134. For quakesM7.0-M7.9, the number lowers to 17. For great quakes of M8.0 or greater, thenumber is near 1.The estimates for M6.0-M6.9 temblors are based upon data since 1990. Otherwise,the dates reflect observations since 1900.
For quakes above M7.0, there has been no important rise in frequency since1900, according to the USGS. But reporting of quakes of M6.0-M6.9 seems to haverisen perceptibly. That lesser earthquakes are reported with increasingfrequency since the establishment of a seismic network likely owes to thecontinuing proliferation of seismic stations around the Earth.
Another important thing to consider is that the timing between natural eventssuch as earthquakes tends to be uneven, with flurries of activity followed byrelative breaks. This owes to the randomness that is inherent in naturalphenomena.
Then, too, there is the matter of perception. A quick succession of majorearthquakes can make headlines and become embedded in memory, but the spells ofrelative quiet are rarely, if ever, borne in mind.
Story by AccuWeather.com Senior Forecaster Jim Andrews.
