Hot spots for world's powerful earthquakes identified

Researchers have pinpointed the locations - like Indonesia's Sumatra Island - where the world's largest earthquakes are most likely to take place, with greater accuracy than ever before.

The 2004 Indian Ocean earthquake had its epicentre off the west coast of Sumatra Island in Indonesia. The resulting tsunami killed over 230,000 people in fourteen countries.
The Pacific 'ring of fire', an area of high earthquake and volcanic activity, and other regions where two tectonic plates converge, are sites for some of the world's largest earthquakes, also known as great earthquakes, researchers said.

"Subduction zones, where one plate slips under another, have long been known to harbour very powerful earthquakes but our research suggests that regions where fracture zones on the seafloor meet subduction zones are at much higher risk," said Dietmar Muller from the University of Sydney.

"The advantage of our new method is that it picks up many of the regions prone to recurring powerful earthquakes over long time periods, including some where no large earthquakes have occurred in the last 100 or so years. Our results could contribute to much-needed improvements of long-term seismic hazard maps," he said.

The coasts of Southern Chile and Peru, Indonesia's Sumatra Island, and several regions along the eastern Eurasian coastline, are some of the regions prone to great earthquakes. The new research shows that regions where subduction zones meet oceanic fracture zones, are at substantially elevated risk of earthquakes 8.4 magnitude or higher.

"We found that 87 per cent of the 15 largest (8.6 magnitude or higher) and half of the 50 largest (8.4 magnitude or higher) earthquakes of the past century are associated with areas of intersection between oceanic fracture zones and subduction zones," said Muller.

The researchers considered about 1500 earthquakes in their study. They used geophysical data, mapping fracture zones and subduction zones, and a database of significant post-1900 events.

They analysed the information by applying a recently developed data mining method previously only used to match Internet users to consumer goods.
The study was published in journal Solid Earth.