Seismograph. When the earth shakes, so does the detector in the seismograph. That wiggles a pen which causes a wavey line as the shocks pass through the detector. GPS is global POSITIONING SYSTEM - maybe when there's a quake it might be picked up by a gps as a small change in the positions of things. anemometers measure fluid flow, such as air wind speeds etc. a volcanometer measures volcanoes ?????
