A rod of single crystalline silicon has been subjected to high-power nanosecond laser pulses inducing ultrasonic and shock waves traveling into the bulk of the material. Stroboscopic time-resolved high-energy x-ray diffraction measurements were carried out in situ to probe for strain states in the bulk of the sample. First, a supersonic shock front is observed which moves faster than the longitudinal acoustic phonons. Following the shock front, a much slower bunch of waves travels along the crystal. The x-ray diffraction records obtained in different configurations reflect a strong dependence of the wave propagation on the sample geometry. These results offer an experimental approach for the investigation of coherent phonons, structural phase transformations, plastic deformations induced during shock peening, and for the development of x-ray free-electron-laser optics.