Unravelling the spatio-temporal nature of rock deformation using 4D X-ray tomography

About the project

Our main question is how to quantify the dynamics of microfractures in rocks to predict the onset of major rupture and earthquake nucleation.

We have developed a combined experimental and numerical approach to unravel how ruptures nucleate in rock samples, how earthquake may damage wall rocks in natural earthquakes, and whether precursory signals exist that would indicate the propagation of an earthquake before it happens. Using dynamic X-ray tomography imaging at the European Synchrotron Facility and a home-designed rock deformation apparatus, the Hades rig, we imaged in 4D the evolution of microfractures in rocks before system-size brittle failure.

12 three-dimensional marble samples showing formation of a fault network, with 12 figures below each of them showing microfracture clusters.
Series of three-dimensional views of a sample of Carrara marble during a creep burst that led to the formation of a fault network under a constant differential stress of 159 MPa. Blue figures show all the microfracture clusters with volumes greater than 104 voxels. At scan 142, the number of microfractures with volume above 104 voxels increases. The system-spanning fault network develops until scan 150 (e.g. creep burst), leading to the formation of an offset along the sample boundary. The time between each scan is 1.7 minutes (Renard et al., 2020).

These microfractures represent precursory signals to the main rupture. Our experiments produce large amounts of data (more than 150 TB so far) and we have developed novel data processing techniques to follow the evolution of strain in a sample during deformation. Among these techniques, we have developed several machine learning workflows to unravel which parameters control the onset of system-size failure in rocks.

Financing

The Research Council of Norway (project HADES, #250661, 2016-2020).

Cooperation

  • The Njord Center, University of Oslo, Norway
  • University Grenoble Alpes, Grenoble, France
  • University of Maryland, USA
  • Temple University, Pennsylvania, USA
  • University of Southern California, USA

Seals of project participants.

 

Publications

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Published Apr. 7, 2021 9:34 AM - Last modified Apr. 23, 2021 3:11 PM