Yes, EARTHQUAKE is a Scrabble word!

Letter values in Scrabble US: E 1, A 1, R 1, T 1, H 4, Q 10, U 1, A 1, K 5, E 1.

Is it a valid word?

EARTHQUAKE is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

shaking and vibration at the surface of the earth resulting from underground movement along a fault plane of from volcanic activity
a disturbance that is extremely disruptive