aftershock vs tremor

aftershock and tremor both are nouns.

Word	Noun	Adjective	Verb	Adverb
aftershock	Yes	No	No	No
tremor	Yes	No	Yes	No

As nouns, tremor is a hypernym of aftershock; that is, tremor is a word with a broader meaning than aftershock:

aftershock: a tremor (or one of a series of tremors) occurring after the main shock of an earthquake
tremor: a small earthquake

Other hypernyms of aftershock include earth tremor, microseism.

aftershock (noun)	tremor (noun)
a tremor (or one of a series of tremors) occurring after the main shock of an earthquake	an involuntary vibration (as if from illness or fear)
	a small earthquake
	shaking or trembling (usually resulting from weakness or stress or disease)

aftershock (verb)	tremor (verb)
	shake with seismic vibrations