That depends. It could be you or the jump if. they gave it more pop and you weren't leaning forward enough. If you didn't know, then it wasn't your fault, but it was your fault for not checking it out first. If you did know, I land really back seat when I get lazy with things.
Anyway, always look at jumps and straight air them first because you never know when things change. I was sent to the hospital because they gave a jump more pop and made it 20ft shorter. I came in way to fast and that's all I remember.