what is the primary tool scientist use to measure earthquakes
The study of seismic waves is known as seismology, a word derived from a Greek word meaning to shake.. Seismographs are the instruments which record earthquakes. Scientists use these instruments as their principal tool to study seismic waves. They are very sensitive instruments that can detect, measure and record ground vibrations and their intensities during an earthquake. A seismograph is a simple pendulum.
A seismometer is the scientific instrument used to detect earthquakes. Signals received from seismometers are recorded and this allows scientists to calculate the size (amount of energy released) of an earthquake, that is, its magnitude.