seism(o)-

An earthquake.

Greek seismos, earthquake.

Seismology is the branch of science concerned with earthquakes and related phenomena; the adjective relating to earthquakes is seismic; a seismograph is an instrument that measures and records earthquakes; the seismicity of a region is the extent to which earthquakes occur there; a seismosaurus was a huge late Jurassic dinosaur (so named because it was so big it must have shaken the earth when it walked).