Scientists have found large earthquakes can trigger aftershocks on the other side of the world.
A study published in the journal Nature found two massive quakes that struck off the coast of Indonesia in April caused a fivefold increase in large earthquakes worldwide for about a week.
A geophysicist with the United States Geological Survey, Fred Pollitz, told Radio New Zealand's Morning Report programme it was previously thought aftershocks could be triggered only over a distance of about 900km.
But the April earthquake triggered large earthquakes 16,093km away in North America.
Dr Pollitz says smaller tremors were also triggered as the seismic waves travelled around the globe.