Global Subduction Zone Map Highlights Regions at Risk of Major Earthquakes

A new map of the world's subduction zones offers clues to the likelihood of a major earthquake occurring by illustrating which regions are capable of generating giant earthquakes and which are not.

The largest earthquakes in the world occur along subduction zones, the meeting point of two tectonic plants where one subducts (or sinks) beneath the other. The magnitude 9.2 earthquake in December 2004 is one of the strongest quakes in recent history. It occurred along a subduction zone off the coast of Sumatra, Indonesia. The earthquake and subsequent tsunami killed more than 200,000 people in 14 countries.

Other recent major earthquakes, including the magnitude 8.8 quake in Chile in 2010 and the magnitude 9.0 earthquake in Japan in 2011, also occurred along subduction zones. Both of these major earthquakes also triggered tsunami that devastated huge swaths of coastline.

To date, scientists have only documented giant earthquakes along a limited number of subduction zone segments. However, such data only goes back to about 1900, and the recurrence time of giant earthquakes can be many hundreds of years.

"The main question is, are all subduction segments capable of generating giant earthquakes, or only some of them? And if only a limited number of them, then how can we identify these," said Wouter Schellart, a geoscientist at Monash University who led the development of the new subduction zone map.

Schellart and his colleagues, including Nick Rawlinson from the University of Aberdeen in Scotland, used earthquake data going back to 1900 and data from subduction zones to map the main characteristics of each of the active subduction zones around Earth. Their mapping revealed that giant earthquakes such as those in Indonesia, Chile and Japan all share commonalities in their physical, geometrical and geological properties.

Among the shared properties are the style of deformation in the plate overlying the subduction zone, the level of geologic stress in the region, the angle at which the tectonic plates are subducting, the curvature of the subduction zone plate boundary and the rate at which it moves.

Based on these indicators, the researchers identified several regions capable of generating giant earthquakes. These regions include Lesser Antilles in the Caribbean, Mexico-Central America tectonic plate boundary, Greece, the Makran region in Pakistan, the Sunda tectonic plate region in Southeast Asia, North Sulawesi in Indonesia and Hikurangi in New Zealand.

"For the Australian region subduction zones of particular significance are the Sunda subduction zone, running from the Andaman Islands along Sumatra and Java to Sumba, and the Hikurangi subduction segment offshore the east coast of the North Island of New Zealand. Our research predicts that these zones are capable of producing giant earthquakes," Schellart said.

"Our work also predicts that several other subduction segments that surround eastern Australia (New Britain, San Cristobal, New Hebrides, Tonga, Puysegur), are not capable of producing giant earthquakes."

The research is published in the open-access journal Physics of the Earth and Planetary Interiors.