World Bulletin / News Desk
Two massive quakes off Indonesia's Sumatra island in April showed something scientists have long been trying to prove - they 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 fivefold globally, lead author Fred Pollitz of the U.S. Geological Survey and colleagues found in a study published in the journal Nature on Thursday.
"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.
"The Pollitz paper shows that you can get significant, potentially destructive-sized earthquakes thousands of kilometres away from a mid-8 earthquake," Sieh, who was not part of the current study, told Reuters.
Pollitz and colleagues examined a range of seismic data, with particular focus on so-called Love-wave radiation, surface waves that move in a snake-like motion and can travel right across the globe.
All the global aftershocks were located right along the four main lines of the Love-wave radiation that began at the epicentre of the main April 11 quake.
In future, studying such data could improve calculations about the increased likelihood of earthquakes after a major quake, said Sieh.
Scientists rushed to analyse the April quakes because they occurred in one of the world's most seismically active zones.
The 2012 quakes are believed by most seismologists to be the largest strike-slip tremors ever recorded, and all the more noteable for not triggering a large tsunami.
Strike-slip faults slide horizontally when they fracture, rather than triggering a sudden uplift of the sea floor like the 9.2 quake that struck off nearby Aceh province in northern Sumatra in December 2004, or last year's 9.0 quake off Japan. Both triggered deadly tsunamis.
Waves of cyberattacks disrupt services for many East Coast US Internet users
Critics slam company after claims it allowed NSA to scan all users’ emails
Shenzhou-11 to take 2 astronauts into space, dock with orbiting space lab Tiangong-2 within 2 days
A German politician has said Facebook should pay for failing to remove online hate comment
For the first time in over 120 years, a design patent case will be heard by the US supreme court.
Toyota is usually associated with cars, but it has been investing millions in robotics and Kirobo is its first commercial foray into the sector.
A joint Mongolian-Japanese expedition found the giant print, which measures 106 centimetres (42 inches) long and 77 centimetres wide.
Current conditions may ‘commit Earth to an eventual total warming of 5 degrees Celsius’ in few thousand years, author says
Cyber-attack in 2014 likely the largest data breach in history
Photographs, videos, polls, quoted tweets no longer count toward 140-character limit
2.5 million phones recalled days before Apple introduces iPhone 7
Mark Zuckerberg has vowed to continue effort to provide satellite for Africa
3.7-billion-year-old rock suggests life began soon after Earth’s formation
Facebook will target advertising to Whatsapp users but will steer clear of third party advertising content
The global seed giant Monsanto is pulling its application to introduce GMO cotton seed after a row with the Indian government, which is demanding the company share its technology with local seed companies.
Proxima b could be visited by spacecraft within next 100 years