Chilean data could help predict size of earthquakes

[SANTIAGO] Closely monitoring land movement along fault lines could help scientists forecast earthquakes and how strong they are likely to be, according to a study that has analysed February’s Chilean earthquake.

Researchers used high-precision global positioning system (GPS) data of earth movements along the fault line where the oceanic Nazca tectonic plate is slipping beneath the continental South America plate. They estimated the amount of strain (the accumulated energy that builds up in rocks) that was released during the 8.8 magnitude earthquake when the fault slipped.

They found that the greatest slippage happened in the areas with the most strain and, since this can be measured by GPS, future earthquake-causing slippages could also be predicted. They reported their findings in Nature last week (9 September).

Until now it was unclear whether these patches of stress that build up along a fault line match the energy released during a later earthquake.

Matthias Rosenau, co-author of the study and a researcher at the GFZ German Research Centre for Geosciences, told SciDev.Net that "the study corroborates [evidence that] the earthquake process, at least along plate boundaries, is a time-dependent process, some components of which could indeed be forecast".

It was the combination of a decade of detailed GPS records and a well-recorded large earthquake — a rare occurrence — that allowed scientists to make this discovery. The data was made available by a network of more than 200 GPS stations set up across Chile between 1996 and 2008.

According to Rosenau, these findings could help pin down where the source of the earthquake is likely to be and how strong an earthquake will result from the build-up of strain caused by plate movements.

"Our findings may help to minimise the uncertainties related to the source and the maximum credible size of future events, and therefore to better assess earthquake and tsunami hazard," he said. "For that to happen, however, similar GPS observations in other earthquake-prone areas are needed.

"We can expect better advice for preparedness in the long term and, in the short term, possibly more accurate early warnings."

Mapping the strain in faults would be useful to prepare for a future event in the long-term, for example, by building earthquake-resistant houses and bridges, and safeguarding slopes in the most hazardous areas, he said.

Jaime Campos, a seismologist at the University of Chile, said the study "confirms that satellite technologies set up in the 1990s in the area [for scientific purposes] captured valuable information about terrestrial deformation and seismicity in the region before the February earthquake".

These findings, Campos added, "have a direct impact in prevention for seismic countries, and open concrete possibilities for implementing these technologies in Chile in the future".