The tarrasque has numerous attacks: bite, claw, etc., etc. None of the stated attacks involve throwing actions, but is it reasonable that the tarrasque could throw a big thing (for instance, a bus,1 or maybe a 1-ton rock) at an attacker? And what would be reasonable for the damage? Strictly by RAW, no throwing things attack is described, but it does not seem like an unreasonable action.
1. I'm picturing your basic city transit bus, but if it makes you feel better feel free to picture a steampunk bus or a medieval wagon or an enchanted slab of rock with chairs on it pulled by pixie day-laborers. Or a flintstone's style prehistoric rock bus. Or a rock the size of a bus. :)