aftershock vs microseism

aftershock and microseism both are nouns.

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

As nouns, microseism is a hypernym of aftershock; that is, microseism 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
microseism: a small earthquake

Other hypernyms of aftershock include earth tremor, tremor.

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