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).
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