Hey! I am having the exact same problem with my neighbors who live above me.
Go up and talk to them politely about keeping the bass turned down when they are jamming out... or at least to keep the bass turned down very late at night. When you go down to speak with them, bring an age appropriate gift; something small to show you appreciate their consent.
Ask them to move the subwoofer on to an end table or to put a towel or pillow underneath the subs. A lot of the vibration you're hearing is coming from directly underneath the sub, vibrating the floors and eventually the walls.
Police intervention should be your final step. Having the police show up to your door when you had no prior signs that your neighbor is upset, is upsetting. No one likes to deal with the police, especially when they are coming to your domicile. Until you have personally spoken with them to offer solutions, be it moving the sub or just turning it down, don't go to the cops.
(When I lived back in Chicago it almost seemed like the guy above me was doing it to piss me off after I asked him to keep it down 4 times. So using carefully selected aggressive language (to avoid any legal claims that I had threatened him) and some stern body language, I "fixed" the problem by freaking him the fuck out and acting like a psycho on his very last straw. Never had another problem again :) I am a very big guy so this may have influenced his decision when I became aggressive.
Number 4 is a last resort. I do not advocate violence but a pseudo-mafia approach can work on some assholes.
"I have work early in the morning and I AM NOT waking up another day tired and irritable due to the music constantly playing."
"You've pushed me entirely too far and I am not going to come up here again and have this conversation, there will be consequences, legal or otherwise."
Good luck! And be sure to assert yourself, you can't have them under the impression you are some kind of punk bitch who can be pushed around. Because this kind of noise is not going to continue if you have anything to do with it.