Acknowledgments, Samples, and Data

This work is supported by the UK’s Natural Environment Research Council (NERC) through the CATFAIL project NE/R001693/1 ‘Catastrophic failure: what controls precursory localization in rocks?’ We acknowledge the beamline PSICHE at SOLEIL for provision of synchrotron radiation facilities (standard proposal 20160434) and thank our reviewers Jess McBeck and Phil Benson for their thoughtful reviews and suggestions. We would also like to thank the University of Edinburgh Geosciences Workshop for their support in developing the experimental apparatus, and Andy Bell for useful discussions about modelling the correlation length evolution. We declare no conflict of interest. The data supporting our conclusions can be found in main text, the Supporting Information and in the μCT datasets held at the NERC repository (http://data.ceda.ac.uk/ngdc/R001693-1). When using the μCT datasets, please cite Cartwright-Taylor et al. (2020) and see https://doi.org/10.5285/0dc00069-8da8-474a-8993-b63ef5c25fb8 for the metadata.