Caveatting the fact that I know nooothing about earthquake-life, I can say that the whole point of attaching things to the studs of a wall is that you can attach heavy, heavy things and they'll stay up. The studs are the big long vertical boards, usually 16" apart from one another, firmly attached to the rest of the house, so they're pretty strong. You can make a shelf strong by attaching it firmly to studs, and attaching it with a good attacher-thing (long screws rather than nails, e.g.), and attaching it to many studs to distribute the load nicely.

That said, all the rentals I know about don't look too kindly at renters drilling into walls. In which case a board-and-cinderblock structure, or similar, is the same principle without the drilling.