Earthquakes

6.9 Earthquake hits the Andreanof Islands near the tip of the Aleutian Island chain off Alaska. No tsunami or damage has been reported, although there is a watch for larger than usual waves.

5.3 Earthquake hits Antofagasta, Chile.

5.1 Earthquake hits south of Fiji.

5.0 Earthquake hits the Kermedec Island region.

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Two massive quakes off Indonesia's Sumatra island in April showed something scientists have long been trying to prove - that large earthquakes can trigger a swarm of more tremors around the globe.

The latest findings could eventually help efforts to predict some earthquakes.

Over the six days after the quakes hit on April 11, the number of tremors of magnitude greater than 5.5 jumped nearly five-fold globally.

"This is the first time that we've seen these remote aftershocks at this magnitude and to this extent," said Kerry Sieh, director of the Earth Observatory of Singapore, author of a number of studies on earthquake hazards in the Sumatra region.

The first quake on April 11 was 8.7 magnitude, nearly as large as the one which triggered a massive tsunami and nuclear disaster in eastern Japan just over a year earlier.

The second one was also huge, at 8.2. Both occurred under the Indian Ocean several hundred kilometres west of Sumatra, in a zone where the Indo-Australian tectonic plate is slowly tearing itself apart.