I'm nitpicking, but you'd think with Attach witnessing the Strawhats party at W7 and fucking MONKEY D GARP telling the HQ MONKEY D LUFFY escaped, the Marine higher ups would have catched them already. Pretty incompetent morons these officers.
They were probably aware that the Straw Hats weren't going anywhere until their log pose set. I'm sure they also know how long it takes the log pose to set on Water 7. After what happened on Enies Lobby, they're probably being very cautious, taking as much time as they can before the log pose sets planning and preparing a way to successfully capture the Straw Hats. That, and you also have to realize that the WG just underwent another crisis, one which takes greater priority over the Straw Hats, where the worlds balance of power was on the line - the Whitebeard-Shanks meeting. I'm sure a good portion of the marine's manpower was dedicated to that crisis. Now that that's over, don't be surprised if something big happens within the next few chapters.