If you remember, Jinbei, being weaker than he is now, was able to fight Ace's logia power on land. Here, we see him "punching from distance" Akainu. The admiral looks like he took the hit, but it couldn't stop him from attack.
Also, Jinbei is protecting Luffy while fighting with Akainu, and because of that he can't fight without any worry. Then he got a magma blast at his back, because he tries to protect Luffy's body from Akainu. His wound is steaming still in page 15, upper panel.