Global broadband network helps analyse Japan earthquake

Understanding the earthquake and subsequent tsunami that struck Japan's east coast earlier this year is easier as global broadband seismography networks are put to the task.

California Institute of Technology has been using broadband-enabled seismographic networks located in different parts of the globe to analyse the movements that occurred in the Earth's crust on March 11th.

They have discovered, for example, that the fault line that shifted measured about 250 km in length - half the distance widely accepted as being involved in earthquakes of such magnitude.

A section of between 50 and 100 km in length marked the greatest shift, with the fault line moving by over 30 m.

Earthquakes are triggered when an area of fault line that has become stressed slips free of the neighbouring tectonic plate, returning to its default position with a pinball-flipper-like motion that sends shock waves through the Earth's outer layers.

"Technology has advanced only in the past ten to 15 years to the point where we can measure these slips much more accurately through global positioning satellites and other data," says Caltech professor of geophysics Mark Simons.