In american irregular usage, it's a known word, but the primary reason someone would use it (other than incidentally or acidentally) is to effect an affect; that is to say, the author might have used this word on purpose to draw your attention.
This type of usage is much more common in, for example, poetical writings; it is also used semifrequently in opinion or persuasive writings. The author Stephen King employs this mechanism very frequently. He loves using weird americanisms to evoke a feeling of alienation from his audiences.
I don't use the word, but I immediately understood it without registering anything strange about it. It didn't seem out of place until I saw this comment thread where I realized it is not actually a word I've ever used. I guess it must be fairly commonly used by (American?) journalists.
I see tremor used often for smallish earthquakes, but not temblor. I guess some journalists like digging up obscure words to pepper through their prose—like The New Yorker, for example.
My (British) dictionary has it asterisked as American and says it derives from Spanish. The definition given is just "earthquake".