An instrument used to detect and record earthquakes is

A seismograph is an instrument that was invented by the scottish physicist James David Forbes in 1842, with the purpose of measuring the movements of Earth's tectonic plates, which cause earthquakes.

The original design of this instrument is based on the principle of inertia (all the bodies have a resistance to movement or to vary their speed); and consisted of a pendulum that remained immobile (due to inertia) during an earthquake while at the end it had a punch that moved along with the ground shake and then recorded all the movements on paper.

However, at present, seismographs have improvements in their functions and it is also possible to determine the epicenter of the earthquake.