Gumbsch and Gao also found that the supersonic speeds only occur when the stress is applied at a single point. At very low strains, the deformations travel subsonically. At intermediate strains, however, they start supersonically but quickly drop below the sound barrier. But if higher strains are applied, stable supersonic deformation occurs, causing a 'shock cone' to ripple throughout the material. Gumbsch and Gao now hope to model these effects on geological features such as tectonic shear faults.