temblor vs earth tremor

temblor and earth tremor both are nouns.

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

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

temblor: 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 temblor include seismic disturbance, shock, microseism, tremor, seaquake, submarine earthquake.

temblor (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