Seismographs are digital instruments used to measure ground vibrations. In order to characterize ground vibrations, data is collected in three independent directions of motion (x, y and z). Seismographs used for blasting and construction vibration monitoring measure ground vibration in terms of particle velocity and operate over a 1 Hz to 250 Hz frequency range. Most vibration criteria developed to prevent damage to offsite structures is set in terms of particle velocity.