Help Still vibrates even when vibrate setting is set to "only in silent mode"?

[Sine17]

Why does it still vibrate when I get a notification even though my vibrate setting is set to "only in silent mode"? It's not in silent mode. Maybe I just didn't notice or feel it before but I'm fairly sure that it didn't vibrate when I got notifications.

 

[Jake-SonyXperia]

Can you advise what notifications make the handset vibrate is this for Facebook or just sms?