Earthquake mechanism discovered

Utrecht University earth scientists and chemists have discovered a mechanism that triggers earthquakes. Their findings, which increase our knowledge of earthquakes, will be published in Science on 11 December.

An earthquake is triggered by two parts of the earth’s crust sliding past each other in a jerky, rather than a smooth way. Despite the huge impact that large earthquakes have on society, the causes of the transition from smooth to jerky movement are still poorly understood. This information  is crucial if we are to improve the models that forecast the size, location and timing of future earthquakes.

Minuscule grains

Earth scientists in the Faculty of Geosciences’ High Pressure and Temperature (HPT) Laboratory at Utrecht University conducted experiments that simulate e fault motion and earthquake generation. In collaboration with chemist Matthijs de Winter from the university’s Faculty of Science they studied the microscopic internal structures developed in the simulated fault zones  using an electron microscope. They discovered that the core of the fault zone consists of thin, planar layers of minute grains of rock “powder”, measuring only tens of thousandths of millimetres. The properties of these "nanoparticles" partly determine how faults slide and whether earthquakes can be generated. 

Long fibres

‘A fault core is generally a very narrow slip zone of between a millimetre and a centimetre thick, and consists of an extremely fine-grained fault gouge’, says main author and earth scientist Bart Verberne. ‘Our research shows that grains of around a tenth of a thousandth of a millimetre in diameter slide past each other, but also form necklace-like chains that slip past each other like long fibres.’

Verberne continues: ‘We have discovered a new aspect of the mechanism underlying the causes of earthquakes. Scientists still do not know exactly how earthquakes work, but our laboratory studies are contributing important information. We have seen many similarities between our findings and what is actually happening in nature.’

Better understanding

The mechanisms discovered by this research are directly applicable to earthquakes in nature, according to Verberne and his colleagues. ‘As well as helping us to understand and model natural earthquakes better, they may also improve our understanding of tremors induced by human activity, such as those currently occurring in Groningen.’

Multi-scale behaviour

Chris Spiers, Professor of Experimental Rock Deformation and Head of the HPT Laboratory, is keen to encourage interfaculty research. ‘This research shows that the mechanisms that are active on a very small scale – the tiny grains and fibres in the slip zone – also control processes on a much larger scale. We call this multi-scale behaviour. We are seeing more and more of these types of effects in many branches of science . Addressing the underlying micro-scale mechanisms is helping us to understand many large phenomena.’

‘The relatively unique collaboration that we have achieved at  Utrecht, between earth scientists, chemists and physicists, is making new advances possible. It is enabling us to study the tiniest nanostructures and so improve our understanding of how processes in the earth’s crust work, as well as how we can design new materials for applications in areas such as catalysis.'

More information

Tom de Kievith MA, Press officer Faculty of Geosciences, +31 30 253 5593,T.deKievith@uu.nl

Monica van der Garde, Press officer Faculty of Science, +31 (0)6 13 66 14 38, m.vandergarde@uu.nl.

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