A seismograph or seismometer is a device that allows the measurement of movements of the earth’s surface, i.e. earthquakes or tremors of any kind. Generally, they are used to measure those produced by the movement of the tectonic or lithospheric plates, in order to carry out studies and predict possible earthquakes. The invention was created by the Scottish James David Forbes in 1842.
The instrument of that time was primitive, and consisted of a pendulum which, because of its mass, remained motionless due to inertia. While all other parts of the machine moved around it. The pendulum had a punch at its end and allowed writing on a roller of time-regulated paper. That way, when the ground vibrated, it was represented on that paper in the form of curves.