With a number of huge earthquakes in recent years -- in Sumatra, Indonesia, in December 2004, Chile in February 2010 and Japan in 2011 --leading many to question whether one large quake can cause another on the other side of the world, Tom Parsons of the U.S. Geological Survey surveyed catalogs of seismic activity on every continent except Antarctica going back to 1979.
Of the 260 earthquakes of magnitude 7 or greater during that period, small earthquakes on separate fault systems followed in the wake of 24 of them, triggered by seismic waves passing through distant lands, he said.
"It's a small hazard, but there is a risk," he said.
Parsons, who presented his results Friday at the Seismological Society of America annual meeting in Salt Lake City, says his next step will be to investigate the 24 quakes that caused far-off events and see if there is anything special about them.
"So far they look fairly ordinary. So we're going to have to really dig into them," he said.