There is no reason for the sudden and dramatic rise in volume. Insider trading? Very possible that some traders have become aware of impending negative news regarding gox and want coins off the exchange. We've been on the edge since the Dwolla news.
... or any other variation on the theme of manipulators and schemers

On the other hand it could just be volumes beginning to return to what was normal (especially considering a much higher proportion is now trading off gox) who were waiting for movement to trade. There is no money to be made from a stagnant (stable) market so from a day trader's perspective it's movement that triggers market action.