Samsung Galaxy s3 still vibrating when getting notification, even though I'm on silent mode I have Samsung Galaxy S3 GT-I9300.

When I put it on silent mode, when I get a notification from Facebook, Facebook Messenger and GMail, or any other notification, it's still vibrating. This is very annoying when I'm in the classroom, for example.

Is there any option to completely disable vibration on silent mode?
This is for Galaxy Nexus, but if you long press the power button, it should create a prompt that allows you to switch between Silent Mode, Vibrate Mode, and Sound Mode.