hire a disk cutter, cut a neat square in your tarmac, till you get through the tarmac, few inches or so.

The hole is best to taper it outwards too, so if they try to yank out the lock, it will be much MUCH harder.

you could also rig up some rebar steel on the base so that it is tied into the conrete far better to.

But after having owned and had stolen, many a motorbike, if they want it, they will have it, so in the end, the system you use has got to be easy and not to inconvenient.

They would most likely just cut a lock shaped hole out of the garage....unless it's a nice thick wooden one.