To determine the strength and location of earthquakes, seismograph is used which is equipped with sensors called seismometers that can detect ground motions causes by seismic waves from both near and distant earthquakes. A seismograph produces wavy lines that reflect the size of seismic waves passing beneath it.
The record of the wave, called a seismogram, is imprinted on paper film or recording tape or is stored and displayed by computes. Probably the best known guage of earthquake intensity is the local Richter magnitude scale, developed in 1935 by
The earliest known seismograph was made in