Researchers Warn Of 'Great Earthquakes'
A group of scientists have found that water pressure in the pores of the rocks making up the plate boundary zone is taking away the key role. They based their findings on the great Chile earthquake of February, 27th, 2010.
Earthquakes occur where oceanic plates move beneath continents and the water trapped in the boundary between both place has a significant influence on the earthquake rupture process.
The stress gradually increases before an earthquake takes place and the magnitude of the subsequent seismic energy release are substantially controlled by the mechanical coupling between plates.
Previously studies have also concluded that in great earthquakes, the lateral extent of the rupture and magnitude are generally controlled by the stress build-up along the subduction plate interface.
"We combined observations of several geoscience disciplines - geodesy, seismology, petrology. In addition, we have a unique opportunity in Chile that our natural observatory there provides us with long time series of data," said Onno Oncken, director of the GFZ-Department "Geodynamics and Geomaterials" in the press release.
Researchers used the GPS technology and radar interferometry that helped them in acquiring a detailed mapping of mechanical coupling of the plate boundary from the Earth's surface.
"For the first time, our results allow us to map the spatial distribution of the fluid pressure with unprecedented resolution showing how they control mechanical locking and subsequent seismic energy release", explained Professor Oncken. "Zones of changed seismic wave speeds reflect zones of reduced mechanical coupling between plates".
The study has been published in the journal Nature Geoscience.