The Magnetic Signature of Stress in Rocks

Magnetic signatures preserved in rocks have long provided insight into Earth’s evolution, revealing processes from plate tectonics to the habitability of Earth. While large impacts are known to impose extreme stresses (>1 GPa) and heat that fundamentally alters magnetic records, lower stresses typical of earthquakes have been considered magnetically undetectable. We show that magnetic responses to sub-GPa stresses can be precisely calibrated, enabling three-dimensional paleostress reconstructions in rocks – even stresses of just a few MPa can fully reset magnetic signals without heat or deformation. This newly revealed magnetic sensitivity to stress opens a powerful, non-destructive pathway to detecting paleostress fields in the elastic crust, offering new opportunities for improving seismic hazard assessment, interpreting impact processes, and re-evaluating magnetic records across Earth and Planetary sciences. -------------------- Data Set S1. Experimentally determined stress - strain curves and magnetic susceptibility data for all the data plotted in the figures. Data Set S2. Experimentally determined Anisotropy of magnetic susceptibility data for all the data plotted in the figures. Data Set S3. Numerically simulated magnetic susceptibility data for all the data plotted in the figures.