The rise in earthquakes is statistically similar to the results of flipping a coin, Parsons said: Sometimes heads or tails will repeat several times in a row, even though the process is random.
"Basically, we can't prove that what we saw during the first part of 2014, as well as since 2010, isn't simply a similar thing to getting six tails in a row," he said.
But Parsons said the statistical findings don't rule out the possibility that the largest earthquakes may trigger one another across great distances. Researchers may simply lack the data to understand such global "communication," he said.
"It's possible that global-level communications happen so infrequently that we haven't seen enough to find it among the larger, rarer events," Parsons said.
However, earthquakes smaller than magnitude-5.6 do cluster on a global scale, the researchers found. This suggests these less-powerful quakes are more likely to be influenced by others - a finding borne out by previous research.
For example, the number of magnitude-5 earthquakes surged after the catastrophic magnitude-9 earthquakes in Japan and Sumatra, even at distances greater than 620 miles (1,000 kilometers), earlier studies found.