22 November 2017

Significant advance in earthquake research

‘Major earthquakes triggered at the microscale’

The processes controlling earthquake nucleation remain enigmatic. Scientists from Utrecht University now found an important piece of the puzzle, claiming that natural earthquakes may be caused by microscale grain rearrangements. The results of their study appeared this week in Nature Communications.

The Earth’s crust is roughly composed of two parts: a ductile deep part and a brittle shallow part. The strongest natural earthquakes often occur at a depth corresponding to the transition zone between ductile and brittle rock. Using unique laboratory equipment, the researchers reproduced fault behaviour at depth conditions simulating this transition zone. The results showed that rearrangements on the scale of a micrometre (= 0.001 millimetre) may lead to an earthquake via some kind of geological snowball-effect.

‘It is not necessarily problematic when two masses of rock in the crust move past each other,’ says Earth scientist and first author Bart Verberne of the High Pressure and Temperature (HPT) laboratory at Utrecht University. ‘As long as grains in the fault rock can deform fast enough there’s no problem. However, when grains deform too slow internally, they have to rearrange. This leads to cavities, which may trigger an instability leading to an earthquake.’

This study enables significant steps in geological research, including into earthquakes

Significant step

These new results constitute an important step in unravelling the processes controlling natural as well as human-induced earthquakes. ‘The combination of experiments with state-of-the-art microscope research, as applied in the present study, enables significant steps in geological research, including into earthquakes‘, Verberne says.

 

This research allows us to better understand natural and human-induced earthquakes, like those that occur in the north of the Netherlands.

Further research

The complexity of the microphysical processes controlling fault rock deformation remain problematic, as well as the challenge of studying them under the pressure and temperature conditions relevant to crustal earthquakes. The research team, which is composed of several others including earthquake scientist André Niemeijer and the head of the HPT laboratory, Chris Spiers, emphasize the need for further research. ‘There are still many pieces of the puzzle missing. Our new results show that experiments with microphysical modelling of fault rock can lead to important new insights’, says Niemeijer. ‘This not only allows us to better understand natural earthquakes, but also the more shallow, human-induced earthquakes, like those that occur in the north of the Netherlands.’

This research was partly funded by an ERC Starting Grant and a VIDI grant from the NWO and Topschool ISES (NWO).