soberness vs seriousness

soberness and seriousness both are nouns.

Word	Noun	Adjective	Verb	Adverb
soberness	Yes	No	No	No
seriousness	Yes	No	No	No

As nouns, seriousness is a hypernym of soberness; that is, seriousness is a word with a broader meaning than soberness:

Other hypernyms of soberness include earnestness, serious-mindedness, sincerity.

soberness (noun)	seriousness (noun)
a manner that is serious and solemn	the trait of being serious
the state of being sober and not intoxicated by alcohol	the quality of arousing fear or distress
	an earnest and sincere feeling