Dynamic synchrotron imaging of brittle failure in crustal rocks

Abstract

Majority of earthquakes originate at depths of 15-20 kilometers and may propagate on to the surface resulting in catastrophes. Predicting their occurrence is an important question in Earth science. These geological phenomena have microstructural origins and can be better understood when considering the material failure properties of rocks at microscale. To investigate microscale deformation in centimetre-scale rock specimen, a special triaxial rock deformation apparatus, HADES (built in-house) is employed. Three-dimensional images of the microstructural deformation at every step increase in axial load are obtained using the technique of synchrotron X-ray micro tomography. A series of digital volumes of the rock microstructure is obtained until failure, which facilitates tracking the accumulation of damage, localization of strain and underlying microstructural mechanisms that govern failure in brittle rocks. Using a detailed analysis of microstructural evolution, this experimental study provide the first test of theoretical models of failure proposed for heterogeneous brittle rocks and identify mechanisms of strain localization and earthquake nucleation in them.