Laboratory experiments examine earthquake precursors



Although it is not possible to predict when an earthquake will occur, many earthquakes have been found to have had some precursor activity. To study precursors of stick-slip behavior, Johnson et al. conducted laboratory experiments on a sheared granular material under normal stress ranging from 2 to 8 megapascals as an analog for a fault under tectonic stress. They found that acoustic emissions and microslips are a precursor to larger movements. Very similar results were obtained in a discrete element simulation of sheared beads. These types of experiments could help scientists better understand when earthquakes are more likely to occur. As shown by a number of researchers, very similar activity preceding faulting can occur in the Earth.