tremor vs aftershock

tremor and aftershock both are nouns.

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

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

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

Other hyponyms of tremor include foreshock.

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

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