First Look
The lap joint around stringer 40 ish will be my first conclusion. Its too far forward 50 inches of main galley so i doubt it would be corrosion from galley, beside when liquid escape from galleys it tends to corrode the floor frames first. Very unlikely to be the wing to body fairings that let go and ripped the fuse as the damage is too far back for that.
Happy to be corrected but this is my initial assessment from the limited visual data, will know more next week.
cheers