seism vs earthquake

seism and earthquake both are nouns.

Word	Noun	Adjective	Verb	Adverb
seism	Yes	No	No	No
earthquake	Yes	No	No	No

As nouns, seism and earthquake are synonyms defined as:

seism and earthquake: shaking and vibration at the surface of the earth resulting from underground movement along a fault plane or from volcanic activity

Other synonyms of seism include quake, temblor.

seism (noun)	earthquake (noun)
shaking and vibration at the surface of the earth resulting from underground movement along a fault plane or from volcanic activity	shaking and vibration at the surface of the earth resulting from underground movement along a fault plane or from volcanic activity
	a disturbance that is extremely disruptive