quake vs earth tremor

quake and earth tremor both are nouns.

Word	Noun	Adjective	Verb	Adverb
quake	Yes	No	Yes	No
earth tremor	Yes	No	No	No

As nouns, earth tremor is a hyponym of quake; that is, earth tremor is a word with a more specific, narrower meaning than quake:

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

Other hyponyms of quake include seismic disturbance, shock, microseism, tremor, seaquake, submarine earthquake.

quake (noun)	earth tremor (noun)
shaking and vibration at the surface of the earth resulting from underground movement along a fault plane or from volcanic activity	a small earthquake

quake (verb)	earth tremor (verb)
shake with fast, tremulous movements
shake with seismic vibrations