How doe a seismograph work?

Answer 1

A seismometer, sometimes known as a seismograph, in modern day is usually inertial an it has:

1) A weight of some kind, called the inertial mass, that moves inside but stays attached.

2) A recording device for the mass.

Basically, the motion in the ground, even very slight, will move this weight and it is the movement of the weight which causes a reading on changes underground.

Some modern systems now use electronics. Instead of a writing device for recording, it uses magnetic strips to record information.

A seismograph records data from an earthquake with a needle and ink. When an earthquake occurs ts records this data and uses the needle with ink on it to show the highs and lows of the P waves, S waves, and surface waves the earthquake produces. The ink lines are recorded on graph paper showing the number of how high or low the earthquake's strength is and measures the waves.