A blasting seismograph is a specialized instrument which measures and records the ground and air vibrations from a blast. A seismograph has two sensors: a geophone (for monitoring ground waves) and a microphone (for monitoring air waves).
- The geophone measures ground motion in three dimensions:
- Vertical: Up and down.
- Longitudinal: Forwards and backwards from the blast.
- Transverse: Side to side.
The microphone measures air overpressure, which is the additional pressure generated by a blast above normal atmospheric pressure.