In a breakthrough, American scientists have developed an earthquake prediction model which will provide a reasonable estimate of the magnitude and location of future quakes.

The forecasting model developed by Danijel Schorlemmer and his team at the University of Southern California College of Letters, Arts and Sciences, aims to predict the rough magnitude and location of future quakes.

While the timing of quakes remains unpredictable, progress on two out of three key questions is significant in the hard discipline of earthquake forecasting, journal Nature reported.

“One of the key aspects in forecasting of earthquakes is stresses. The findings in the paper help identify locations that are highly stressed from readily available earthquake catalogues,” Schorlemmer said.

Seismologists believe that the build-up of stress deep in the earth causes earthquakes. Monitoring such stress has proven impossible to date.

The team observed that different types of earthquakes differ on average in the stresses needed for rupture. Quakes from thrust faults, which push a large block of earth upward, require the largest stress.

Quakes on normal faults, in which two plates pull apart and a block of earth drops, require the least stress.

Quakes on strike-slip faults such as the San Andreas, where two plates slide past each other, fall somewhere in the middle.

The researchers then noticed that two laws of statistical seismology -- those governing the relative frequency of big and small quakes, and the decay in time of aftershocks -- differ slightly for each type of earthquake.

Regions with active thrust faults tend to have a greater proportion of large quakes than regions with normal faults, with strike—slip faults falling in the middle.

The number of aftershocks from quakes on thrust faults tends to start decaying sooner than the number of aftershocks near normal faults, with strike-slips faults again somewhere in between.

Schorlemmer realised that these differences could be applied productively: One could study the relative frequency and aftershock patterns of small to medium sized earthquakes -- which occur regularly in every seismically active region -- and infer the level of stress in different parts of that region.

That realisation led to a new earthquake prediction model.

“We are observing the little aftershocks all over California, deriving the state of stress and trying to predict the future main shocks,” Schorlemmer said.

The model is now being tested by the Collaboratory for the Study of Earthquake Predictability (CSEP).

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