Most Powerful Earthquake Zones Identified

Since earthquake generation is a very complex process, the scientists don’t yet have a complete understanding of why great earthquakes prefer the intersection areas. They suggest that it is due to the physical properties of fracture zones, which result in “strong, persistent coupling in the subduction boundaries,” Landgrebe explains. This means that the subduction fault area is locked and thus capable of accumulating stress over long periods of time.

“The connection we have uncovered provides critical information for seismologists to, in the long run, pinpoint particular tectonic environments that are statistically more prone to strong seismic coupling and great earthquake supercycles,” Müller says. An area with earthquake supercycles experiences recurring powerful earthquakes every few centuries or millennia.

Regions that have long earthquake supercycles are usually not picked up as risk areas by seismic hazard maps as these are constructed mainly using data collected after 1900. An example is the area of the 2011 Tohoku-Oki earthquake, which had no record of large earthquakes over the past century and was not predicted to be of significant risk by previous hazard maps.

“The power of our new method is that it does pick up many of these regions and, hence, could contribute to much-needed improvements of long-term seismic hazard maps,” Müller explains.

“Even though we don’t fully understand the physics of long earthquake cycles, any improvements that can be made using statistical data analysis should be considered as they can help reduce earthquake damage and loss of life.”

The floor of the Earth’s oceans is crossed by underwater mountain systems, or ocean ridges, such as the mid-Atlantic ridge that runs from north to south between the Americas and Africa. These ridges divide two tectonic plates that move apart as lava emerges from the opening, spreading the sea floor. The mid-ocean ridge jogs back and forth at offsets known as transform faults, creating zig-zagged plate boundaries. Fracture zones are scars in the ocean floor left by these transform faults.
More information

This research is presented in the paper ‘The link between great earthquakes and the subduction of oceanic fracture zones’ published in the EGU Open Access journal Solid Earth on 05 December 2012.

The scientific article is available online at: http://www.solid-earth.net/3/447/2012/se-3-447-2012.html

The discussion paper (not peer-reviewed) and reviewers comments is available at http://www.solid-earth-discuss.net/4/1229/2012/sed-4-1229-2012.html

The team is composed of Dietmar Müller and Thomas Landgrebe, both of the EarthByte Group, School of Geosciences, University of Sydney (Australia).