Predictors of brain injury, such as the head injury criterion, rely on external measurements of head motion. Direct measurements of brain motion could more accurately predict brain injury. Current methods of estimating brain deformation fail to provide the high frame-rates necessary to characterize the fast transient events asso- ciated with traumatic brain injury. We have developed novel ultrasonic methods and motion tracking algorithms that can generate high frame-rate (up to 10,000 images/second) movies that quantify brain motion with a high displacement sensitivity (better than 1 micron). We propose to use this technique to image and quantify shear shock wave propagation in the ex vivo and in vivo brain. Preliminary data is presented, showing for the rst time, shear shock wave propagation in the brain. The violent gradients in shear shock waves may tear and damage neurons thus causing diffuse axonal injuries. We propose to characterize the nonlinear properties of the brain and to develop nonlinear simulations of shear shock wave propagation in the brain. We propose animal experiments in conjunction with histological analysis to establish a link between these rapid events and injury. We propose simulations in conjunction with measurements of head acceleration to predict injuries and concussions. If successful, this research could transform how we view the mechanics of trauma in the brain and be applied to traumatic injuries anywhere in the body.