What is a person who studies earthquakes called?

A person who studies earthquakes is called a seismologist. Seismologists study earthquakes by using seismographs and by venturing into the field to view the damage caused by an earthquake.

Seismographs are instruments that record the vibrations of the Earth’s surface caused by seismic waves. Chang Heng invented the first seismograph in A.D. 132 and called the instrument an earthquake weathercock. This instrument featured eight dragons, each with a bronze ball in its mouth. Whenever a tremor occurred, a mechanism within the seismograph would cause one of the dragon's mouths to open. The ball fell into one of the toad's mouths, providing an alert for an earthquake.