From Nature:
Seismologists debate whether the recent spate of megaquakes is a statistical fluke or something more.
Beginning in late 2004, a flurry of massive, tsunami-spawning earthquakes have rocked the world, first slamming Indonesia, then Chile and most recently Japan. Temblors that size are rare indeed: only 7 quakes as large or larger than 8.8 — the magnitude of last February's Chilean event — have occurred since 1900.
So what does it mean that three of those seven shocks have happened almost within the span of six years? While some scientists argue that these 'megaquakes' could be the vanguard of an extended outburst of strong seismic events, many others suggest that the apparent cluster of recent temblors is nothing more than a statistical fluke."Are all the recent big earthquakes connected? " (and Joe Granville stops by)
The recent spate of far-flung quakes is remarkably similar to a cluster that occurred in the middle of the last century, says Charles Bufe, a seismologist retired from the US Geological Survey (USGS) in Denver, Colorado. The seismic events in that supposed grouping, consisting of 3 magnitude 9 or higher temblors, struck Kamchatka, then Chile and then Alaska within a 12-year interval. The odds of quakes that large occurring randomly within such a short time span is only four per cent, Bufe noted today at the annual meeting of the Seismological Society of America in Memphis, Tennessee.
In an update to an analysis first published in June 2005, Bufe and colleague David Perkins, a USGS geophysicist also in Denver, argue that the most recent round of large temblors may mark the beginning of a new global outbreak of megaquakes. According to their model, Bufe says, the probability of another quake of magnitude 9 or larger striking in the next 6 years is about 63 per cent. "There's now an increased hazard situation for these very large earthquakes," he notes....MORE
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