what detects an earthquake
In contrast, modern seismometers detect and convert any small movement in the Earth into an electrical signal for use in computer systems, as shown in the digital seismogram image of five seismic sensors which detected the magnitude 5.4 earthquake near Moe in Victoria on 19 June 2012. Earthquakes are detected by scientific instruments called seismometers. The word seismo originates from the Greek word seismos which means to shake or move violently and was later applied to the science and equipment associated with earthquakes.