"On your head" seems to be a bit older slang. You could take it to mean "your fault", but the phrase with which I'm more familiar goes like this "if you do a such-and-such stupid thing, and such-and-such bad thing happens, on your head be it," meaning, "if you do something stupid, the consequences are your own fault." A bit old-timey.

As a native speaker, I have never heard the phrase "This is on your head" before. If you want to say something similar to "This is your fault", in a very informal way, you can say "That's on you". An example would be me saying "I had to stay at work until midnight" and my colleague could say "Well, you came in around lunch-time, so that's on you".

We don't normally say 'this is on your head' as a standalone. We would tend to use it in the sort of context that artie delphi goo mentioned, in advising somebody else against a certain course of action 'if you do x, on your head be it'. It is talking about possible future consequences of the advised against action, stating that the person concerned would be to blame for them. 'This is your fault' is used when something negative has already happened and somebody is being held responsible.

"On your head" is British it means. If anything goes wrong you will be responsible. Sometimes you will hear people say"OK on your head be it" or similar variations after failing to reach an agreement. So yes they would be the same. after something had gone wrong, or somebody made a mistake. Then you would say to them "this is your fault" or "this is on your head" . Example Your friend drives a car whilst drunk and maims somebody, they ask you to cover for them. You reply "NO this is on your head"

They have the same meaning, but "This is on your head." is more casual/is slang... You could use it when talking to friends. When talking to your boss, your parents, people to whom you should give respect... maybe you should use neither.